Microbiology - First Aid Flashcards
Bacterial Appendages:
- made of proteins
- motility
Flagellum
Bacterial Appendages:
- made of glycoproteins
- mediate adherence of bacteria to cell surface
- sex pilus forms during conjugation
Pilus/Fimbria
Bacterial Structures:
- has a keratin-like coat
- made of dipicolinic acid, peptidoglycan and DNA
- gram ⊕ only
- resists dehydration, heat, and chemicals
Spore
Bacterial Cell Envelope:
- has an organized, discrete polysaccharide layer (except poly-d-glutamate on B anthracis)
- protects against phagocytosis
Capsule
Bacterial Cell Envelope:
- loose network of polysaccharides
- mediates adherence to surfaces, especially foreign surfaces (eg. indwelling catheters)
Glycocalyx
Bacterial Cell Envelope:
- Outer Leaflet: contains endotoxin (LPS/LOS)
- Embedded Proteins: porins and other outer membrane proteins (OMPs)
- Inner Leaflet: phospholipids
- gram ⊝ only
- Endotoxin: lipid A induces TNF and IL-1, antigenic O polysaccharide component
- most OMPs are antigenic
- Porins: transport across outer membrane
Outer Membrane
Bacterial Cell Envelope:
- space between cytoplasmic membrane and outer membrane in gram ⊝ bacteria (peptidoglycan in middle)
- accumulates components exiting gram ⊝ cells, including hydrolytic enzymes (eg. β-lactamases)
Periplasm
Bacterial Cell Envelope:
- peptidoglycan is a sugar backbone with peptide side chains cross-linked by transpeptidase
- net-like structure gives rigid support
- protects against osmotic pressure damage
Cell Wall
Bacterial Cell Envelope:
- phospholipid bilayer sac with embedded proteins (eg. penicillin-binding proteins [PBPs]) and other enzymes
- lipoteichoic acids (gram ⊕ only) extend from membrane to exterior
- site of oxidative and transport enzymes
- PBPs involved in cell wall synthesis
- lipoteichoic acids induce TNF-α and IL-1
Cytoplasmic Membrane
Bacterial Cell Envelope
Bacterial Taxonomy:
spherical
Coccus
Bacterial Taxonomy:
rod
Bacillus
Bacterial Taxonomy:
no cell wall
Pleomorphic
Bacterial Taxonomy:
spiral
Spirochete
Bacterial Taxonomy:
Gram ⊕ Cocci
- Staphylococcus (clusters)
- Streptococcus (chains or pairs)
- Enterococcus (pairs or short chains)
Bacterial Taxonomy:
Gram ⊝ Cocci
- Moraxella catarrhalis
- Neisseria
Bacterial Taxonomy:
Gram ⊕ Bacilli
- Bacillus
- Clostridium
- Corynebacterium
- Gardnerella (gram variable)
- Lactobacillus
- Listeria
- Mycobacterium (acid fast)
- Cutibacterium (formerly Propionibacterium)
Bacterial Taxonomy:
Enteric Gram ⊝ Bacilli
- Bacteroides
- Campylobacter
- E. coli
- Enterobacter
- Fusobacterium
- Helicobacter
- Klebsiella
- Proteus
- Pseudomonas
- Salmonella
- Serratia
- Shigella
- Vibrio
- Yersinia
Bacterial Taxonomy:
Respiratory Gram ⊝ Bacilli
- Acinetobacter baumannii
- Bordetella
- Burkholderia cepacia
- Haemophilus (pleomorphic)
- Legionella (silver stain)
Bacterial Taxonomy:
Zoonotic Gram ⊝ Bacilli
- Bartonella
- Brucella
- Francisella
- Pasteurella
Bacterial Taxonomy:
Branching Filamentous Gram ⊕ Bacteria
- Actinomyces
- Nocardia (weakly acid fast)
Bacterial Taxonomy:
Pleomorphic Gram ⊝ Bacteria
- Anaplasma
- Ehrlichia
- Chlamydiae (Giemsa)
- Rickettsiae (Giemsa)
- Mycoplasma (contains sterols, which do no Gram stain)
- Ureaplasma
Bacterial Taxonomy:
Gram ⊝ Spirochetes
- Borrelia (Giemsa)
- Leptospira
- Treponema
Bacterial Taxonomy:
Staphylococcus
Gram ⊕ Cocci in clusters
Bacterial Taxonomy:
Streptococcus
Gram ⊕ Cocci in chains or pairs
Bacterial Taxonomy:
Enterococcus
Gram ⊕ Cocci in pairs or short chains
Bacterial Taxonomy:
Moraxella catarrhalis
Gram ⊝ Cocci
Bacterial Taxonomy:
Neisseria
Gram ⊝ Cocci
Bacterial Taxonomy:
Bacillus
Gram ⊕ Bacilli
Bacterial Taxonomy:
Clostridium
Gram ⊕ Bacilli
Bacterial Taxonomy:
Corynebacterium
Gram ⊕ Bacilli
Bacterial Taxonomy:
Gardnerella
Gram ⊕ Bacilli
*gram variable
Bacterial Taxonomy:
Lactobacillus
Gram ⊕ Bacilli
Bacterial Taxonomy:
Listeria
Gram ⊕ Bacilli
Bacterial Taxonomy:
Mycobacterium
Acid Fast Gram ⊕ Bacilli
Bacterial Taxonomy:
Cutibacterium (formerly Propionibacterium)
Gram ⊕ Bacilli
Bacterial Taxonomy:
Bacteroides
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
Campylobacter
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
E. coli
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
Enterobacter
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
Fusobacterium
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
Helicobacter
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
Klebsiella
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
Proteus
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
Pseudomonas
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
Salmonella
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
Serratia
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
Shigella
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
Vibrio
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
Yersinia
Enteric Gram ⊝ Bacilli
Bacterial Taxonomy:
Acinetobacter baumannii
Respiratory Gram ⊝ Bacilli
Bacterial Taxonomy:
Bordetella
Respiratory Gram ⊝ Bacilli
Bacterial Taxonomy:
Burkholderia cepacia
Respiratory Gram ⊝ Bacilli
Bacterial Taxonomy:
Haemophilus
Pleomorphic Respiratory Gram ⊝ Bacilli
Bacterial Taxonomy:
Legionella
Respiratory Gram ⊝ Bacilli
*silver stain
Bacterial Taxonomy:
Bartonella
Zoonotic Gram ⊝ Bacilli
Bacterial Taxonomy:
Brucella
Zoonotic Gram ⊝ Bacilli
Bacterial Taxonomy:
Francisella
Zoonotic Gram ⊝ Bacilli
Bacterial Taxonomy:
Pasteurella
Zoonotic Gram ⊝ Bacilli
Bacterial Taxonomy:
Actinomyces
Branching Filamentous Gram ⊕ Bacteria
Bacterial Taxonomy:
Nocardia
Branching Filamentous Gram ⊕ Bacteria
*weakly acid fast
Bacterial Taxonomy:
Anaplasma
Pleomorphic Gram ⊝ Bacteria
Bacterial Taxonomy:
Ehrlichia
Pleomorphic Gram ⊝ Bacteria
Bacterial Taxonomy:
Chlamydiae
Pleomorphic Gram ⊝ Bacteria
*Giemsa
Bacterial Taxonomy:
Rickettsiae
Pleomorphic Gram ⊝ Bacteria
*Giemsa
Bacterial Taxonomy:
Mycoplasma
Pleomorphic Gram ⊝ Bacteria
*contains sterols, which do not Gram stain
Bacterial Taxonomy:
Ureaplasma
Pleomorphic Gram ⊝ Bacteria
Bacterial Taxonomy:
Borrelia
Gram ⊝ Spirochetes
*Giemsa
Bacterial Taxonomy:
Leptospira
Gram ⊝ Spirochetes
Bacterial Taxonomy:
Treponema
Gram ⊝ Spirochetes
Stains:
first-line lab test in bacterial identification
Gram Stain
- Gram ⊕—thick peptidoglycan layer retains crystal violet dye
- Gram ⊝—thin peptidoglycan layer turns red or pink with counterstain
_____ do not Gram stain well.
These Little Microbes May Unfortunately Lack Real Color But Are Everywhere
- Treponema—too thin
- Leptospira—too thin
- Mycobacteria—cell wall has high lipid content
- Mycoplasma—no cell wall
- Ureaplasma—no cell wall
- Legionella—intracellular
- Rickettsia—intracellular
- Chlamydia—intracellular, lacks classic peptidoglycan because of ↓ muramic acid
- Bartonella—intracellular
- Anaplasma—intracellular
- Ehrlichia—intracellular
_____ are seen through Giemsa stain.
Ricky got Chlamydia as he Tried to Please the Bored “Geisha.”
- Rickettsia
- Chlamydia
- Trypanosomes
- Plasmodium
- Borrelia
Stains:
- stains glycogen and mucopolysaccharides
- used to diagnose Whipple disease (Tropheryma whipplei)
Periodic Acid–Schiff Stain
PASs the sugar.
Stains:
- acid-fast bacteria (eg. Mycobacteria, Nocardia; stains mycolic acid in cell wall)
- protozoa (eg. Cryptosporidium oocysts)
Ziehl-Neelsen Stain
*Auramine-Rhodamine Stain is more often used for screening (inexpensive, more sensitive).
(Carbol Fuchsin)
Stains:
- seen through India ink stain
- Mucicarmine can also be used to stain thick polysaccharide capsule red
Cryptococcus neoformans
Stains:
- fungi (eg. Coccidioides, Pneumocystis jirovecii)
- Legionella
- Helicobacter pylori
Silver Stain
Stains:
- used to identify many bacteria and viruses
- FTA-ABS for syphilis
Fluorescent Antibody Stain
Properties of Growth Media:
- favors the growth of particular organism while preventing growth of other organisms
- eg. Thayer-Martin agar contains antibiotics that allow the selective growth of Neisseria by inhibiting the growth of other sensitive organisms
Selective Media
Properties of Growth Media:
- yields a color change in response to the metabolism of certain organisms
- contains a pH indicator
- a lactose fermenter like E. coli will convert lactose to acidic metabolites → color change
- eg. MacConkey agar
Indicator (Differential) Media
Special Culture Requirements:
H. influenzae
Chocolate agar
- Factor V (NAD+)
- Factor X (hematin)
Special Culture Requirements:
N. gonorrhoeae, N. meningitidis
Thayer-Martin agar
- selectively favors growth of Neisseria by inhibiting growth of gram ⊕ organisms with Vancomycin, gram ⊝ organisms except Neisseria with Trimethoprim and Colistin, and fungi with Nystatin
Very Typically Cultures Neisseria
Special Culture Requirements:
B. pertussis
- Bordet-Gengou agar (Bordet for Bordetella)
- potato extract
- Regan-Lowe medium
- charcoal
- blood
- antibiotic
Special Culture Requirements:
C. diphtheriae
- Tellurite agar
- Löffler medium
Special Culture Requirements:
M. tuberculosis
Löwenstein-Jensen agar
Special Culture Requirements:
M. pneumoniae
Eaton agar
- requires cholesterol
Special Culture Requirements:
Lactose-Fermenting Enterics
MacConkey agar
- fermentation produces acid causing colonies to turn pink
Special Culture Requirements:
E. coli
Eosin–Methylene Blue (EMB) agar
- colonies with green metallic sheen
Special Culture Requirements:
Legionella
Charcoal Yeast Extract agar
- buffered with cysteine and iron
_____ use an O2-dependent system to generate ATP.
Aerobes
Aerobes
Nagging Pests Must Breathe.
- Nocardia
- Pseudomonas aeruginosa
- MycoBacterium tuberculosis
Reactivation of M .tuberculosis (eg. after immunocompromise or TNF-α inhibitor use) has a predilection for the _____.
apices of the lung
____ lack catalase and/or superoxide dismutase and are thus susceptible to oxidative damage. Generally foul smelling (short-chain fatty acids), are difficult to culture, and produce gas in tissue (CO2 and H2).
Anaerobes
Anaerobes
Anaerobes Can’t Breathe Fresh Air.
- Clostridium
- Bacteroides
- Fusobacterium
- Actinomyces israelii
Anaerobes are normal flora in the _____, typically pathogenic elsewhere.
GI tract
_____ are ineffective against anaerobes becaus these antibiotics require O2 to enter into bacterial cell.
Aminoglycosides
AminO2glycosides
_____ may use O2 as a terminal electron acceptor to generate ATP, but can also use fermentation and other O2-independent pathways.
Facultative Anaerobes
Facultative Anaerobes
- Streptococci
- Staphylococci
- Enteric Gram ⊝ Bacteria
Obligate Intracellular Bacteria
Stay inside (cells) when it is Really CHilly and COld.
- Rickettsia
- CHlamydia
- COxiella
*rely on host ATP
Facultative Intracellular Bacteria
Some Nasty Bugs May Live FacultativeLY.
- Salmonella
- Neisseria
- Brucella
- Mycobacterium
- Listeria
- Francisella
- Legionella
- Yersinia pestis
The capsules of _____ serve as an antiphagocytic virulence factor. They are opsonized, and then cleared by spleen. Capsular polysaccharide + protein conjugate serves as an antigen in vaccines.
Encapsulated Bacteria
Encapsulated Bacteria
Please SHiNE my SKiS.
- Pseudomonas aeruginosa
- Streptococcus pneumoniae
- Haemophilus influenzae type b
- Neisseria meningitidis
- Escherichia coli
- Salmonella
- Klebsiella pneumoniae
- Group B Strep.
Asplenics have ↓ opsonizing ability and thus ↓ risk for severe infections; need vaccines to protect against _____.
No Spleen Here
- N. meningitidis
- S. pneumoniae
- H. influenzae
_____ containing polysaccharide capsule antigens are conjugated to a carrier protein, enhancing immunogenicity by promoting T-cell activation and subsequent class switching. A polysaccharide antigen alone cannot be presented to T cells.
Encapsulated Bacteria Vaccines
Encapsulated Bacteria Vaccines
- Pneumococcal vaccines:
- PCV13 (pneumococcal conjugate vaccine)
- PPSV23 (pneumococcal polysaccharide vaccine with no conjugated protein)
- H. influenzae type b (conjugate vaccine)
- Meningococcal vaccine (conjugate vaccine)
Urease-Positive Organisms
Pee CHUNKSS
- Proteus
- Cryptococcus
- H. pylori
- Ureaplasma
- Nocardia
- Klebsiella
- S. epidermidis
- S. saprophyticus
*predisposes to struvite (ammonium magnesium phosphate) stones, particularly Proteus
_____ hydrolyzes urea to release ammonia and CO2 → ↑ pH.
Urease
_____ degrades H2O2 into H2O and bubbles of O2 before it can be converted to microbicidal products by the enzyme myeloperoxidase.
Catalase
People with _____ (NADPH oxidase deficiency) have recurrent infections with certain catalase ⊕ organisms.
Chronic Granulomatous Disease
Catalase-Positive Organisms
Cats Need PLACESS to Belch their Hairballs.
- Nocardia
- Pseudomonas
- Listeria
- Aspergillus
- Candida
- E. coli
- Staphylococci
- Serratia
- B. cepacia
- H. pylori
Pigment-Producing Bacteria:
yellow “sulfur” granules—composed of filaments of bacteria
Actinomyces israelii
Israel has yellow sand.
Pigment-Producing Bacteria:
yellow pigment
S. aureus
Aureus (Latin) = gold
Pigment-Producing Bacteria:
blue-green pigment (pyocyanin and pyoverdin)
P. aeruginosa
Aerugula is green.
Pigment-Producing Bacteria:
red pigment
Serratia marcescens
red Sriracha hot sauce
In Vivo Biofilm Producing Bacteria:
catheter and prosthetic device infections
S. epidermidis
In Vivo Biofilm Producing Bacteria:
- dental plaques
- infective endocarditis
Viridans streptococci
- S. mutans
- S. sanguinis
In Vivo Biofilm Producing Bacteria:
- respiratory tree colonization in patients with cystic fibrosis
- ventilator-associated pneumonia
- contact lens–associated keratitis
P. aeruginosa
In Vivo Biofilm Producing Bacteria:
otitis media
Nontypeable (Unencapsulated) H. influenzae
_____ promote evasion of host immune response.
Bacterial Virulence Factors
Bacterial Virulence Factors:
- binds Fc region of IgG
- prevents opsonization and phagocytosis
- expressed by S. aureus
Protein A
Bacterial Virulence Factors:
- enzyme that cleaves IgA, allowing bacteria to adhere to and colonize mucous membranes
- secreted by S. pneumoniae, H. influenzae type b, and Neisseria
IgA protease
SHiN
- S. pneumoniae
- H. influenzae type b
- Neisseria
Bacterial Virulence Factors:
- helps prevent phagocytosis
- expressed by group A streptococci
- shares similar epitopes to human cellular proteins (molecular mimicry)
- possibly underlies the autoimmune response seen in acute rheumatic fever
M protein
_____ is also known as “injectisome.” It’s a needle-like protein appendage facilitating direct delivery of toxins from certain gram ⊝ bacteria (eg. Pseudomonas, Salmonella, Shigella, E. coli) to eukaryotic host cell.
Type III Secretion System
Bacterial Genetics:
- competent bacteria can bind and import short pieces of environmental naked bacterial chromosomal DNA (from bacterial cell lysis)
- transfer and expression of newly transferred genes
- a feature of many bacteria, especially S. pneumoniae, H. influenzae type b, and Neisseria
- adding deoxyribonuclease degrades naked DNA, preventing _____
Transformation
Bacterial Genetics:
Conjugation (F+ × F–)
- F+ plasmid contains genes required for sex pilus and conjugation
- bacteria without this plasmid are termed F–
- sex pilus on F+ bacterium contacts F− bacterium
- a single strand of plasmid DNA is transferred across the conjugal bridge (“mating bridge”)
- no transfer of chromosomal DNA
Bacterial Genetics:
Conjugation (Hfr × F–)
- F+ plasmid can become incorporated into bacterial chromosomal DNA, termed High-frequency recombination (Hfr) cell
- transfer of leading part of plasmid and a few flanking chromosomal genes
- High-frequency recombination may integrate some of those bacterial genes
- recipient cell remains F– but now may have new bacterial genes
Bacterial Genetics:
- a packaging “error”
- lytic phage infects bacterium, leading to cleavage of bacterial DNA
- parts of bacterial chromosomal DNA may become packaged in phage capsid
- phage infects another bacterium, transferring these genes
Generalized Transduction
Bacterial Genetics:
- an “excision” event
- lysogenic phage infects bacterium
- viral DNA incorporates into bacterial chromosome
- when phage DNA is excised, flanking bacterial genes may be excised with it
- DNA is packaged into phage capsid and can infect another bacterium
Specialized Transduction
*Genes for the following 5 bacterial toxins are encoded in a lysogenic phage (ABCD’S):
- Group A strep erythrogenic toxin
- Botulinum toxin
- Cholera toxin
- Diphtheria toxin
- Shiga toxin
Bacterial Genetics:
- segment of DNA (eg. transposon) that can “jump” (copy/excise and reinsert) from one location to another, can transfer genes from plasmid to chromosome and vice versa
- this is a critical process in creating plasmids with multiple antibiotic resistance which can be transferred across species lines (eg. Tn1546 carrying vanA gene from vancomycin-resistant Enterococcus to S. aureus)
Transposition
Bacterial Genetics:
- formed by some bacteria when nutrients are limited
- lack metabolic activity
- highly resistant to heat and chemicals
- core contains dipicolinic acid
- must autoclave to kill by steaming at 121°C for 15 minutes
Spores
Spore-Forming Bacteria
- Bacillus anthracis—anthrax
- Bacillus cereus—food poisoning
- Clostridium botulinum—botulism
- Clostridium difficile—pseudomembranous colitis
- Clostridium perfringens—gas gangrene
- Clostridium tetani—tetanus
Exotoxins:
Source
certain species of gram ⊕ and gram ⊝ bacteria
Exotoxins:
Cell Secretion
yes
Exotoxins:
Chemical Composition
Polypeptide
Exotoxins:
Location of Genes
- Plasmid
- Bacteriophage
Exotoxins:
Adverse Effects
High
*fatal dose on the order of 1 μg
Exotoxins:
Clinical Effects
Varied
Exotoxins:
Mode of Action
Varied
Exotoxins:
Antigenicity
induces high-titer antibodies called antitoxins
Exotoxins:
Vaccines
Toxoids
Exotoxins:
Heat Stability
destroyed rapidly at 60°C (except staphylococcal enterotoxin and E. coli heatstable toxin)
Exotoxins:
Typical Diseases
- Tetanus
- Botulism
- Diphtheria
Endotoxins:
Source
outer cell membrane of most gram ⊝ bacteria
Endotoxins:
Cell Secretion
No
Endotoxins:
Chemical Composition
Lipid A component of LPS (structural part of bacteria; released when lysed)
Endotoxins:
Location of Genes
Bacterial Chromosome
Endotoxins:
Adverse Effects
Low
*fatal dose on the order of hundreds of micrograms
Endotoxins:
Clinical Effects
- fever
- shock (hypotension)
- DIC
Endotoxins:
Mode of Action
induces TNF, IL-1, and IL-6
Endotoxins:
Antigenicity
poorly antigenic
Endotoxins:
Vaccines
- no toxoids formed
- no vaccine available
Endotoxins:
Heat Stability
stable at 100°C for 1 hr
Endotoxins:
Typical Diseases
- Meningococcemia
- Sepsis by gram ⊝ rods
Exotoxins:
- two-component toxin (or three for anthrax) with B enabling binding and triggering uptake (endocytosis) of the active A component
- the A components are usually ADP ribosyltransferases; others have enzymatic activities
AB toxin
Exotoxins:
inhibit protein synthesis
- Corynebacterium diphtheriae—Diphtheria toxin
- Pseudomonas aeruginosa—Exotoxin A
- Shigella spp.—Shiga toxin (ST)
- Enterohemorrhagic E. coli—Shiga-like toxin (SLT)
Exotoxins:
- AB toxin
- inactivate elongation factor (EF-2)
- pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck)
Corynebacterium diphtheriae—Diphtheria toxin
Exotoxins:
- AB toxin
- inactivate elongation factor (EF-2)
- host cell death
Pseudomonas aeruginosa—Exotoxin A
Exotoxins:
- AB toxin
- inactivate 60S ribosome by removing adenine from rRNA
- GI mucosal damage → dysentery
- enhances cytokine release, causing hemolyticuremic syndrome (HUS)
Shigella spp.—Shiga toxin (ST)
Exotoxins:
- AB toxin
- inactivate 60S ribosome by removing adenine from rRNA
- enhances cytokine release, causing HUS (prototypically in EHEC serotype O157:H7).
- unlike Shigella, EHEC does not invade host cells
Enterohemorrhagic E. coli—Shiga-like toxin (SLT)
Exotoxins:
increase fluid secretion
- Enterotoxigenic E. coli
- Heat-labile toxin (LT)
- Heat-stable toxin (ST)
- Bacillus anthracis—Edema toxin
- Vibrio cholerae—Cholera toxin
Exotoxins:
- AB toxin
- overactivates adenylate cyclase (↑ cAMP) → ↑ Cl− secretion in gut and H2O efflux
- watery diarrhea
Enterotoxigenic E. coli—Heat-labile toxin (LT)
Labile in the Air (Adenylate cyclase)
Exotoxins:
- overactivates guanylate cyclase (↑ cGMP) → ↓ resorption of NaCl and H2O in gut
- watery diarrhea
Enterotoxigenic E. coli—Heat-stable toxin (ST)
Stable on the Ground (Guanylate cyclase)
Exotoxins:
- AB toxin
- mimics adenylate cyclase (↑ cAMP)
- likely responsible for characteristic edematous borders of black eschar in cutaneous anthrax
Bacillus anthracis—Edema toxin
Exotoxins:
- AB toxin
- overactivates adenylate cyclase (↑ cAMP) by permanently activating Gs → ↑ Cl− secretion in gut and H2O efflux
- voluminous “rice-water” diarrhea
Vibrio cholerae—Cholera toxin
Exotoxins:
inhibit phagocytic ability
Bordetella pertussis—Pertussis toxin
Exotoxins:
- overactivates adenylate cyclase (↑ cAMP) by disabling Gi, impairing phagocytosis to permit survival of microbe
- Whooping Cough—child coughs on expiration and “whoops” on inspiration (toxin may not actually be a cause of cough; can cause “100-day cough” in adults)
Bordetella pertussis—Pertussis toxin
Exotoxins:
inhibit release of neurotransmitter
- Clostridium tetani—Tetanospasmin
- Clostridium botulinum—Botulinum toxin
Exotoxins:
- AB toxin
- protease that cleaves SNARE (soluble NSF attachment protein receptor), a set of proteins required for neurotransmitter release via vesicular fusion
- prevents release of inhibitory (GABA and glycine) neurotransmitters from Renshaw cells in spinal cord → spastic paralysis, risus sardonicus, trismus (lockjaw)
Clostridium tetani—Tetanospasmin
Exotoxins:
- AB toxin
- protease that cleaves SNARE (soluble NSF attachment protein receptor), a set of proteins required for neurotransmitter release via vesicular fusion
- prevents release of stimulatory (ACh) signals at neuromuscular junction → flaccid paralysis (floppy baby)
Clostridium botulinum—Botulinum toxin
Exotoxins:
lyse cell membranes
- Clostridium perfringens—Alpha toxin
- Streptococcus pyogenes—Streptolysin O
Exotoxins:
- phospholipase (lecithinase) that degrades tissue and cell membranes
- degradation of phospholipids → myonecrosis (“gas gangrene”) and hemolysis (“double zone” of hemolysis on blood agar)
Clostridium perfringens—Alpha toxin
Exotoxins:
- protein that degrades cell membrane
- lyses RBCs
- contributes to β-hemolysis
- host antibodies against toxin (ASO) used to diagnose rheumatic fever
Streptococcus pyogenes—Streptolysin O
Exotoxins:
superantigens causing shock
- Staphylococcus aureus—Toxic Shock Syndrome toxin (TSST-1)
- Streptococcus pyogenes—Erythrogenic exotoxin A
Exotoxins:
- cross-links β region of TCR to MHC class II on APCs outside of the antigen binding site → overwhelming release of IL-1, IL-2, IFN-γ, and TNF-α → shock
- Toxic Shock Syndrome: fever, rash, shock
Staphylococcus aureus—Toxic Shock Syndrome toxin (TSST-1)
Exotoxins:
- cross-links β region of TCR to MHC class II on APCs outside of the antigen binding site → overwhelming release of IL-1, IL-2, IFN-γ, and TNF-α → shock
- Toxic Shock–like Syndrome: fever, rash, shock;
scarlet fever
Streptococcus pyogenes—Erythrogenic exotoxin A
Endotoxin
ENDOTOXINS:
- Edema
- Nitric oxide
- DIC/Death
- Outer membrane
- TNF-α
- O-antigen + core polysaccharide + lipid A
- eXtremely heat stable
- IL-1 and IL-6
- Neutrophil chemotaxis
- Shock
_____ are the glycolipid LPS molecules found in the outer membrane of gram ⊝ bacteria (both cocci and rods).
Endotoxins
Endotoxins are composed of _____.
- O antigen
- core polysaccharide
- lipid A—toxic component
Endotoxins are released upon _____ or by living cells by _____ (vs. exotoxin, which is actively secreted).
- cell lysis
- blebs detaching from outer surface membrane
The three main effects of endotoxins are _____.
- macrophage activation (TLR4/CD14)
- complement activation
- tissue factor activation
Gram-Positive Lab Algorithm
Gram-Positive Cocci Antibiotic Test:
Staphylococci
Novobiocin
- Saprophyticus is Resistant
- Epidermidis is Sensitive
On the office’s “staph” retreat, there was No StRESs.
Gram-Positive Cocci Antibiotic Test:
Streptococci
Optochin
- Viridans is Resistant
- Pneumoniae is Sensitive
OVRPS (overpass)
Bacitracin
- group B strep are Resistant
- group A strep are Sensitive
B-BRAS.
_____ are gram ⊕ cocci which partially reduce hemoglobin causing greenish or brownish color without clearing around growth on blood agar.
α-Hemolytic Bacteria
α-Hemolytic Bacteria
-
Streptococcus pneumoniae
- catalase ⊝
- optochin sensitive
- Viridans streptococci
- catalase ⊝
- optochin resistant
_____ are gram ⊕ cocci which cause complete lysis of RBCs → clear area surrounding colony on blood agar.
β-Hemolytic Bacteria
β-Hemolytic Bacteria
-
Staphylococcus aureus
- catalase and coagulase ⊕
-
Streptococcus pyogenes
- group A strep
- catalase ⊝ and bacitracin sensitive
-
Streptococcus agalactiae
- group B strep
- catalase ⊝ and bacitracin resistant
Bacteria:
- Gram ⊕
- β-hemolytic
- Catalase ⊕
- Coagulase ⊕
- cocci in clusters
- Protein A (virulence factor) binds Fc-IgG, inhibiting complement activation and phagocytosis
- commonly colonizes the nares, ears, axilla, and groin
Staphylococcus aureus
Bacteria:
- Inflammatory Disease—skin infections, organ abscesses, pneumonia (often after influenza virus infection), endocarditis, septic arthritis, and osteomyelitis
- Toxin-Mediated Disease—toxic shock syndrome (TSST-1), scalded skin syndrome (exfoliative toxin), rapid-onset food poisoning (enterotoxins)
Staphylococcus aureus
Bacteria:
- important cause of serious nosocomial and community-acquired infections
- resistant to methicillin and nafcillin because of altered penicillin-binding protein
MRSA (Methicillin-Resistant S. aureus)
_____ is a superantigen that binds to MHC II and T-cell receptor, resulting in polyclonal T-cell activation.
TSST-1
_____ causes fever, vomiting, rash, desquamation, shock, and end-organ failure. It results in ↑ AST, ↑ ALT, ↑ bilirubin. Associated with prolonged use of vaginal tampons or nasal packing.
Staphylococcal Toxic Shock Syndrome (TSS)
_____ causes a toxic shock–like syndrome associated with painful skin infection.
Streptococcus pyogenes
_____ food poisoning due to ingestion of preformed toxin → short incubation period (2–6 hr) followed by nonbloody diarrhea and emesis. Enterotoxin is heat stable → not destroyed by cooking.
S. aureus
Bad _____ make coagulase and toxins. Forms fibrin clot around self abscess.
S. aureus
Bacteria:
- Gram ⊕
- Catalase ⊕
- Coagulase ⊝
- Urease ⊕
- cocci in clusters
- Novobiocin sensitive
- does not ferment mannitol
- normal flora of skin
- contaminates blood cultures
- infects prosthetic devices (eg. hip implant, heart valve) and IV catheters by producing adherent biofilms
Staphylococcus epidermidis
Bacteria:
- Gram ⊕
- Catalase ⊕
- Coagulase ⊝
- Urease ⊕
- cocci in clusters
- Novobiocin resistant
- normal flora of female genital tract and perineum
- second most common cause of uncomplicated UTI in young women (most common is E. coli)
Staphylococcus saprophyticus
Bacteria:
- Gram ⊕
- lancet-shaped diplococci
- encapsulated
- IgA protease
- Optochin sensitive
- associated with “rusty” sputum, sepsis in patients with sickle cell disease, and asplenic patients
- no virulence without capsule
Streptococcus pneumoniae
Bacteria:
most common cause of meningitis, otitis media (in children), pneumonia, and sinusitis
Streptococcus pneumoniae
MOPS spread pneumonia.
- Meningitis
- Otitis media (in children)
- Pneumonia
- Sinusitis
Bacteria:
- Gram ⊕
- α-hemolytic cocci
- resistant to optochin
- normal flora of the oropharynx
Viridans Group Streptococci
Viridans group strep live in the mouth, because they are not afraid of-the-chin (op-to-chin resistant).
Viridans Group Streptococci:
cause dental caries
- Streptococcus mutans
- SStreptococcus mitis
Viridans Group Streptococci:
makes dextrans that bind to fibrin-platelet aggregates on damaged heart valves, causing subacute bacterial endocarditis
Streptococcus sanguinis
Sanguinis = blood.
Think, “there is lots of blood in the heart” (endocarditis).
Bacteria:
- Gram ⊕ cocci in chains
- Bacitracin sensitive
- β-hemolytic
- Pyrrolidonyl Arylamidase (PYR) ⊕
- Hyaluronic acid capsule and M protein inhibit phagocytosis
- antibodies to M protein enhance host defense but can give rise to rheumatic fever
Streptococcus pyogenes (Group A Streptococci)
Bacteria:
- Pyogenic—pharyngitis, cellulitis, impetigo (“honey-crusted” lesions), erysipelas
- Toxigenic—scarlet fever, toxic shock–like syndrome, necrotizing fasciitis
- Immunologic—rheumatic fever, glomerulonephritis
Streptococcus pyogenes (Group A Streptococci)
ASO titer or anti-DNase B antibodies indicate recent _____ infection.
Streptococcus pyogenes (Group A Streptococci)
_____ pharyngitis can result in rheumatic fever and glomerulonephritis.
Streptococcus pyogenes (Group A Streptococci)
Pharyngitis can result in rheumatic “phever” and glomerulonephritis.
_____ strains causing impetigo can induce glomerulonephritis.
Streptococcus pyogenes (Group A Streptococci)
_____ causes blanching, sandpaper-like body rash, strawberry tongue, and circumoral pallor in the setting of group A streptococcal pharyngitis (erythrogenic toxin ⊕).
Scarlet Fever
Bacteria:
- Gram ⊕ cocci
- Bacitracin resistant
- β-hemolytic
- colonizes vagina
- causes pneumonia, meningitis, and sepsis, mainly in babies.
- produces CAMP factor, which enlarges the area of hemolysis formed by S. aureus. (Note: CAMP stands for the authors of the test, not cyclic AMP.)
- Hippurate test ⊕
- PYR ⊝
Streptococcus agalactiae (Group B Streptococci)
Group B is β-hemolytic for Babies.
Pregnant women should be screened for _____ at 35–37 weeks of gestation with rectal and vaginal swabs.
Streptococcus agalactiae (Group B Streptococci)
Patients with ⊕ _____ culture should receive intrapartum penicillin prophylaxis.
Streptococcus agalactiae (Group B Streptococci)
Bacteria:
- Gram ⊕ cocci
- colonizes the gut
- S. gallolyticus (_____ biotype 1) can cause bacteremia and subacute endocarditis and is associated with colon cancer
Streptococcus bovis
Bovis in the Blood = Cancer in the Colon
Bacteria:
- Gram ⊕ cocci
- Penicillin G resistant
- Catalase ⊝
- PYR ⊕
- normal colonic flora that cause UTI, biliary tract infections, and subacute endocarditis (following GI/GU procedures)
- VRE (vancomycin-resistant _____) are an important cause of nosocomial infection
- more resilient than streptococci, can grow in 6.5% NaCl and bile (lab test)
Enterococci
- E. faecalis
- E. faecium
Bacteria:
- Gram ⊕
- spore-forming rod
- produces anthrax toxin
- the only bacterium with a polypeptide capsule (contains d-glutamate)
- colonies show a halo of projections, sometimes referred to as “medusa head” appearance
Bacillus anthracis
_____ causes painless papule surrounded by vesicles → ulcer with black eschar ( A ) (painless, necrotic) → uncommonly progresses to bacteremia and death.
Cutaneous Anthrax
(Bacillus anthracis)
_____ is caused by inhalation of _____ spores → flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, and shock. Also known as woolsorter’s disease. CXR may show widened mediastinum.
Pulmonary anthrax
(Bacillus anthracis)
Bacteria:
- Gram ⊕ rod.
- causes food poisoning
- spores survive cooking rice (also known as reheated rice syndrome)
- keeping rice warm results in germination of spores and enterotoxin formation
-
Emetic Type
- usually seen with rice and pasta
- nausea and vomiting
- onset within 1–5 hr
- caused by cereulide, a preformed toxin
-
Diarrheal Type
- watery, nonbloody diarrhea and GI pain
- onset within 8–18 hr
Bacillus cereus
Bacteria:
- Gram ⊕
- spore-forming
- obligate anaerobic rods
Clostridia (with exotoxins)
Bacteria:
- produces tetanospasmin, an exotoxin causing tetanus
- causes spastic paralysis, trismus (lockjaw), risus sardonicus (raised eyebrows and open grin), and opisthotonos (spasms of spinal extensors)
Clostridium tetani
_____ are proteases that cleave SNARE proteins for
neurotransmitters. They blocks release of inhibitory neurotransmitters, GABA and glycine, from Renshaw cells in spinal cord.
- Tetanus toxin
- Botulinum toxin
Tetanus is treated with _____.
- Antitoxin +/− Vaccine Booster
- Antibiotics
- Diazepam (for muscle spasms)
- Wound Debridement
Bacteria:
- produces a heat-labile toxin that inhibits ACh release at the neuromuscular junction, causing botulism
- in adults, disease is caused by ingestion of preformed toxin
- in babies, ingestion of spores (eg. in honey) leads to disease (floppy baby syndrome)
- local botox injections used to treat focal dystonia, achalasia, and muscle spasms
- used for cosmetic reduction of facial wrinkles
Clostridium botulinum
Botulinum is from bad bottles of food, juice, and honey (causes a descending flaccid paralysis).
The symptoms of botulism are _____.
4 D’s:
- Diplopia
- Dysarthria
- Dysphagia
- Dyspnea
Botulism is treated with _____.
Human Botulinum Immunoglobulin
Bacteria:
- produces α toxin (lecithinase, a phospholipase) that can cause myonecrosis (gas gangrene; presents as soft tissue crepitus) and hemolysis
- spores can survive in undercooked food
- when ingested, bacteria release heat-labile enterotoxin → food poisoning.
Clostridium perfringens
Perfringens perforates a gangrenous leg.
Bacteria:
- produces 2 toxins
-
Toxin A
- enterotoxin,
- binds to brush border of gut and alters fluid secretion
-
Toxin B
- cytotoxin
- disrupts cytoskeleton via actin depolymerization
- both toxins lead to diarrhea → pseudomembranous colitis
- often 2° to antibiotic use, especially Clindamycin or Ampicillin
- associated with PPIs
Clostridium difficile
Difficile causes diarrhea.
Clostridium difficile is diagnosed by _____.
- PCR
- antigen detection of one or both toxins in stool
Clostridium difficile is treated with _____.
- Metronidazole
- Oral Vancomycin
Recurrent Clostridium difficile is treated with _____.
- consider repeating prior regimen
- Fidaxomicin
- Fecal Microbiota Transplant
Bacteria:
- Gram ⊕ rod
- black colonies on cystine-tellurite agar
- transmitted via respiratory droplets
- causes diphtheria via exotoxin encoded by β-prophage
- potent exotoxin inhibits protein synthesis via ADP-ribosylation of EF-2
- symptoms include pseudomembranous pharyngitis (grayish-white membrane) with lymphadenopathy, myocarditis, and arrhythmias
- lab diagnosis based on gram ⊕ rods with metachromatic (blue and red) granules and ⊕ Elek test for toxin
- toxoid vaccine prevents diphtheria
Corynebacterium diphtheriae
Coryne = club shaped
ABCDEFG:
- ADP-ribosylation
- β-prophage
- Corynebacterium
- Diphtheriae
- Elongation Factor 2
- Granules
Bacteria:
- Gram ⊕
- facultative intracellular rod
- acquired by ingestion of unpasteurized dairy products and cold deli meats, via transplacental transmission, or by vaginal transmission during birth
- grows well at refrigeration temperatures (4°–10°C; “cold enrichment”)
Listeria monocytogenes
Bacteria:
- forms “rocket tails” via actin polymerization that allow intracellular movement and cell-to-cell spread across cell membranes, thereby avoiding antibody
- characteristic tumbling motility in broth
Listeria monocytogenes
Bacteria:
- amnionitis, septicemia, and spontaneous abortion in pregnant women
- granulomatosis infantiseptica
- neonatal meningitis
- meningitis in immunocompromised patients
- mild, selflimited gastroenteritis in healthy individuals
Listeria monocytogenes
Listeria monocytogenes is treated with _____.
Ampicillin
Bacteria:
- gram ⊕
- form long, branching filaments resembling fungi
- Nocardia
- Actinomyces
Bacteria:
- aerobe
- acid fast (weak)
- found in soil
- causes pulmonary infections in immunocompromised (can mimic TB but with ⊝ PPD)
- cutaneous infections after trauma in immunocompetent
- can spread to CNS
- treated with sulfonamides (TMP-SMX)
Nocardia
Bacteria:
- anaerobe
- not acid fast
- normal oral, reproductive, and GI flora
- causes oral/facial abscesses that drain through sinus tracts
- often associated with dental caries/extraction and other maxillofacial trauma
- forms yellow “sulfur granules”
- can cause PID with IUDs
- treated with Penicillin
Actinomyces
Nocardia is treated with _____ while Actinomyces is treated with _____.
SNAP:
- Sulfonamides—Nocardia
- A**ctinomyces—P**enicillin
Mycobacteria:
- causes TB
- often resistant to multiple drugs
Mycobacterium tuberculosis
Mycobacteria:
- causes disseminated, non-TB disease in AIDS
- often resistant to multiple drugs
- prophylaxis with azithromycin when CD4+ count < 50 cells/mm3
Mycobacterium avium–intracellulare
Mycobacteria:
cervical lymphadenitis in children
Mycobacterium scrofulaceum
Mycobacteria:
hand infection in aquarium handlers
Mycobacterium marinum
All mycobacteria are _____ organisms (pink rods).
acid-fast
TB symptoms include _____.
- fever
- night sweats
- weight loss
- cough (nonproductive or productive)
- hemoptysis
_____ creates a “serpentine cord” appearance in virulent M. tuberculosis strains; activates macrophages (promoting granuloma formation) and induces release of TNF-α.
Cord Factor
_____ (surface glycolipids) inhibit phagolysosomal fusion.
Sulfatides
Tuberculosis
Tuberculosis:
PPD __ if current infection or past exposure.
PPD ⊕
Tuberculosis:
PPD __ if no infection and in sarcoidosis or HIV infection (especially with low CD4+ cell count).
PPD ⊝
Tuberculosis:
has fewer false positives from BCG vaccination
Interferon-γ Release Assay (IGRA)
Characteristics of 2° Tuberculosis include _____.
- Caseating Granulomas with central necrosis
- Langhans Giant Cells
Mycobacteria:
- caused by Mycobacterium leprae, an acid-fast bacillus that likes cool temperatures (infects skin and superficial nerves—“glove and stocking” loss of sensation) and cannot be grown in vitro
- diagnosed via skin biopsy or tissue PCR
- reservoir in US: armadillos
Leprosy (Hansen disease)
Leprosy:
- presents diffusely over the skin, with leonine (lion-like) facies
- communicable (high bacterial load)
- characterized by low cell-mediated immunity with a humoral Th2 response
- can be lethal
Lepromatous
Lepromatous form can be Lethal.
Leprosy:
- limited to a few hypoesthetic, hairless skin plaques
- characterized by high cell-mediated immunity with a largely Th1-type immune response and low bacterial load
Tuberculoid
Leprosy (Hansen disease) is treated with _____.
- Tuberculoid
- Dapsone
- Rifampin
- Lepromatous
- Lofazimine
- Dapsone
- Rifampin
Gram-Negative Lab Algorithm
Bacteria:
- Gram ⊝ diplococci
- metabolizes glucose
- produces IgA proteases
- contains lipooligosaccharides (LOS) with strong endotoxin activity
Neisseria
Bacteria:
- no polysaccharide capsule
- often intracellular (within neutrophils)
- Maltose not fermented
- no vaccine due to antigenic variation of pilus proteins
- sexually or perinatally transmitted
- causes gonorrhea, septic arthritis, neonatal conjunctivitis (2–5 days after birth), pelvic inflammatory disease (PID), and Fitz-Hugh-Curtis syndrome
- condoms ↓ sexual transmission
Neisseria gonorrhoeae
Gonococci ferment Glucose.
_____ eye ointment prevents neonatal blindness from Neisseria gonorrhoeae.
Erythromycin
Neisseria gonorrhoeae is treated with _____.
Ceftriaxone (+ Azithromycin or Doxycycline, for possible chlamydial coinfection)
Bacteria:
- polysaccharide capsule
- Maltose fermentation
- vaccine (type B vaccine not widely available)
- transmitted via respiratory and oral secretions
- causes meningococcemia with petechial hemorrhages and gangrene of toes, meningitis, Waterhouse-Friderichsen syndrome (adrenal insufficiency, fever, DIC, shock)
Neisseria meningitidis
MeninGococci ferment Maltose and Glucose.
_____ are given to close contacts as prophylaxis for Neisseria meningitidis.
- Rifampin
- Ciprofloxacin
- Ceftriaxone
Neisseria meningitidis is treated with _____.
- Ceftriaxone
- Penicillin G
Bacteria:
- small gram ⊝ (coccobacillary) rod
- aerosol transmission
- nontypeable (unencapsulated) strains are the most common cause of mucosal infections (otitis media, conjunctivitis, bronchitis) as well as invasive infections since the vaccine for capsular type b was introduced
- produces IgA protease
Haemophilus influenzae
Bacteria:
- culture on chocolate agar, which contains factors V (NAD+) and X (hematin) for growth;
- can also be grown with S. aureus, which provides factor V via RBC hemolysis
Haemophilus influenzae
Bacteria:
- epiglottitis
- “cherry red” in children
- “thumb sign” on lateral neck x-ray
- meningitis
- otitis media
- pneumonia
Haemophilus influenzae
HaEMOPhilus
- Epiglottitis
- Meningitis
- Otitis media
- Pneumonia
Haemophilus influenzae is treated with _____.
- Amoxicillin +/− Clavulanate–mucosal infections
- Ceftriaxone–meningitis
- Rifampin–prophylaxis for close contacts
Bacteria:
- vaccine contains type b capsular polysaccharide (polyribosylribitol phosphate) conjugated to diphtheria toxoid or other protein
- given between 2 and 18 months of age
Haemophilus influenzae
Bacteria:
- Gram ⊝
- aerobe
- coccobacillus
-
Virulence Factors
- Pertussis toxin (disables Gi)
- Adenylate Cyclase toxin (↑ cAMP)
- Tracheal Cytotoxin
- may be mistaken as viral infection due to lymphocytic infiltrate resulting from immune response
Bordetella pertussis
Stages of Pertussis
- Catarrhal—low-grade fevers, Coryza
- Paroxysmal—paroxysms of intense cough followed by inspiratory “whooP” (“whooping cough”), posttussive vomiting
- Convalescent—gradual recovery of chronic cough
Pertussis is prevented by _____ vaccines.
- Tdap
- DTaP
Bacteria:
- Gram ⊝ rod
- Gram stains poorly
- seen on silver stain
- grows on charcoal yeast extract medium with iron and cysteine
- detected by presence of antigen in urine
- labs may show hyponatremia
- aerosol transmission
Legionella pneumophila
Think of a French legionnaire (soldier) with his silver helmet, sitting around a campfire (charcoal) with his iron dagger—he is no sissy (cysteine).
Legionella pneumophila causes _____ which presents with severe pneumonia (often unilateral and lobar), fever, GI and CNS symptoms. Common in smokers and in chronic lung disease.
Legionnaires’ disease
_____ is mild flu-like syndrome caused by Legionella pneumophila.
Pontiac Fever
Legionella pneumophila is treated with _____.
- Macrolide
- Quinolone
Bacteria:
- Gram ⊝ rod
- aerobic
- motile
- Oxidase ⊕
- non-lactose fermenting
- found in water
- grape-like odor
Pseudomonas aeruginosa
Bacteria:
- mucoid polysaccharide capsule may contribute to chronic pneumonia in cystic fibrosis patients due to biofilm formation
- corneal ulcers/keratitis in contact lens wearers/minor eye trauma.
Pseudomonas aeruginosa
Pseudomonas aeruginosa is associated with _____.
PSEUDOMONAS:
- Pneumonia
- Sepsis
- Ecthyma gangrenosum
- UTIs
- Diabetes
- Osteomyelitis
- Mucoid polysaccharide capsule
- Otitis externa (swimmer’s ear)
- Nosocomial infections (eg. catheters, equipment)
- Addicts (drug abusers)
- Skin infections (eg. hot tub folliculitis, wound infection in burn victims).
_____ is a rapidly progressive, necrotic cutaneous lesion caused by Pseudomonas bacteremia. Typically seen in immunocompromised patients.
Ecthyma Gangrenosum
Pseudomonas aeruginosa is treated with _____.
CAMPFIRE:
- Carbapenems
- Aminoglycosides
- Monobactams
- Polymyxins (eg. polymyxin B, colistin)
- Fluoroquinolones (eg. ciprofloxacin, levofloxacin)
- ThIRd- and fourth-generation cephalosporins (eg. ceftazidime, cefepime)
- Extended-spectrum penicillins (eg. piperacillin, ticarcillin)
Bacteria:
- Gram ⊝ rod
- non-lactose fermenting
- Oxidase ⊝
- can invade the GI tract via M cells of Peyer patches
- Salmonella
- Shigella
Bacteria:
- Reservoir: humans only
- can disseminate hematogenously
- produces H2S
- has flagella
-
Virulence Factors
- Endotoxin
- Vi Capsule
-
Infectious Dose (ID50)
- High—large inoculum required
- acid-labile (inactivated by gastric acids)
Salmonella typhi
Bacteria:
- monocytic immune response
- causes constipation, followed by diarrhea
- causes typhoid fever (rose spots on abdomen, constipation, abdominal pain, fever)
- carrier state with gallbladder colonization
- antibiotics prolong duration of fecal excretion
Salmonella typhi
Salmonella typhi vaccines are _____.
- Oral vaccine—live attenuated S. typhi
- IM vaccine—Vi capsular polysaccharide
Salmonella typhi is treated with _____.
- Ceftriaxone
- Fluoroquinolone
Bacteria:
- Reservoir: humans and animals
- can disseminate hematogenously
- produces H2S
- has flagella
- Virulence Factor: Endotoxin
- Infectious Dose (ID50): High
Salmonella spp.
(except S. typhi)
Bacteria:
- PMNs in disseminated disease
- causes diarrhea (possibly bloody)
- no vaccine
- poultry, eggs, pets, and turtles are common sources
- gastroenteritis is usually caused by nontyphoidal species
- antibiotics not indicated
- antibiotics prolong duration of fecal excretion
Salmonella spp.
(except S. typhi)
Bacteria:
- Reservoir: humans only
- cell to cell spread
- does not produce H2S
- no flagella
-
Virulence Factor:
- Endotoxin
- Shiga toxin (Enterotoxin)
-
Infectious Dose (ID50):
- Low—very small inoculum required
- acid stable (resistant to gastric acids)
Shigella
Bacteria:
- PMN infiltration
- causes bloody diarrhea (bacillary dysentery)
- no vaccine
-
Species in order of decreasing severity (less toxin produced):
- S. dysenteriae
- S. flexneri
- S. boydii
- S. sonnei
- invasion of M cells is key to pathogenicity
- organisms that produce little toxin can cause disease
- antibiotics shorten duration of fecal excretion
Shigella
Four F’s:
- Fingers
- Flies
- Food
- Feces
Bacteria:
- Gram ⊝ rod
- usually transmitted from pet feces (eg. puppies), contaminated milk, or pork
- causes acute diarrhea or pseudoappendicitis (right lower abdominal pain due to mesenteric adenitis and/or terminal ileitis)
Yersinia enterocolitica
Bacteria:
- MacConkey agar—pink colonies
- EMB agar—purple/black colonies
Lactose-Fermenting Enteric Bacteria
Lactose-Fermenting Enteric Bacteria
Lactose is key. Test with MacConKEE’S agar.
- Citrobacter
- Klebsiella
- E. coli
- Enterobacter
- Serratia (weak fermenter)
E. coli produces _____, which breaks down lactose into glucose and galactose.
β-galactosidase
_____ grows colonies with a green sheen.
E. coli
Bacteria:
- Gram ⊝ rod
-
Virulence Factors:
- Fimbriae—cystitis and pyelonephritis (P-pili)
- K Capsule—pneumonia, neonatal meningitis
- LPS Endotoxin—septic shock
Escherichia coli
E. coli Strains:
- microbe invades intestinal mucosa and causes necrosis and inflammation
- dysentery
- clinical manifestations similar to Shigella
Enteroinvasive E. coli (EIEC)
E. coli Strains:
- produces heat-labile and heat-stable enterotoxins
- no inflammation or invasion
- Traveler’s Diarrhea (watery)
Enterotoxigenic E. coli (ETEC)
ETEC = Traveler’s Diarrhea
E. coli Strains:
- no toxin produced
- adheres to apical surface
- flattens villi
- prevents absorption
- diarrhea, usually in children
Enteropathogenic E. coli (EPEC)
EPEC = Pediatrics
E. coli Strains:
- O157:H7 is most common serotype in US
- transmitted via undercooked meat, raw leafy vegetables
- Shiga-like toxin causes Hemolytic-Uremic
- Syndrome
- dysentery (toxin alone causes necrosis and inflammation)
- does not ferment Sorbitol (vs. other E. coli)
Enterohemorrhagic E. coli (EHEC)
EHEC = Hemorrhagic, Hamburgers, HUS
EHEC produces Shiga-like toxin which causes _____: triad of anemia, thrombocytopenia, and acute renal failure due to microthrombi forming on damaged endothelium → mechanical hemolysis (with schistocytes on peripheral blood smear), platelet consumption, and ↓ renal blood flow.
Hemolytic-Uremic Syndrome (HUS)
Bacteria:
- Gram ⊝ rod
- intestinal flora that causes lobar pneumonia in alcoholics and diabetics when aspirated
- very mucoid colonies caused by abundant polysaccharide capsules
- dark red “currant jelly” sputum (blood/mucus)
- nosocomial UTI
- associated with evolution of multidrug resistance (MDR)
Klebsiella
5 A’s of KlebsiellA:
- Aspiration pneumonia
- Abscess in lungs and liver
- Alcoholics
- DiAbetics
- “CurrAnt jelly” sputum
Bacteria:
- Gram ⊝
- comma or S shaped (with polar flagella)
- Oxidase ⊕
- grows at 42°C
- major cause of bloody diarrhea, especially in children
- fecal-oral transmission through person-to-person contact or via ingestion of undercooked contaminated poultry or meat, unpasteurized milk
- contact with infected animals (dogs, cats, pigs) is a risk factor
- common antecedent to Guillain-Barré syndrome and reactive arthritis
Campylobacter jejuni
Campylobacter likes the hot campfire.
Bacteria:
- Gram ⊝
- flagellated
- comma shaped
- Oxidase ⊕
- grows in alkaline media
- endemic to developing countries
- produces profuse rice-water diarrhea via enterotoxin that permanently activates Gs, ↑ cAMP
- sensitive to stomach acid (acid labile)
- requires large inoculum (high ID50) unless host has ↓ gastric acidity
- transmitted via ingestion of contaminated water or uncooked food (eg. raw shellfish)
- treat promptly with oral rehydration solution
Vibrio cholerae
Bacteria:
- Gram ⊝ rod
- curved
- flagellated (motile)
-
Triple ⊕:
- Catalase ⊕
- Oxidase ⊕
- Urease ⊕
- urea breath test or fecal antigen test are used for diagnosis
- Urease produces ammonia, creating an alkaline environment, which helps survival in acidic mucosa
- colonizes mainly antrum of stomach
- causes gastritis and peptic ulcers (especially duodenal)
- risk factor for pepti ulcer disease, gastric adenocarcinoma, and MALT lymphoma
Helicobacter pylori
Helicobacter pylori is treated with triple therapy which includes _____.
Antibiotics Cure Pylori.
- Amoxicillin (Metronidazole for Penicillin allergy)
- Clarithromycin
- Proton Pump Inhibitor
Bacteria:
- spiral-shaped
- axial filaments
Spirochetes
Spirochetes
BLT
- B**orrelia (big size)—B**orrelia is Big
- Leptospira
- Treponema
Among the spirochetes, only _____ can be visualized using aniline dyes (Wright or Giemsa stain) in light microscopy due to size.
Borrelia
Treponema is visualized by _____.
- Dark-Field Microscopy
- Direct Fluorescent Antibody (DFA) Microscopy
Bacteria:
- Lyme disease
- transmitted by the Ixodes deer tick (also
- vector for Anaplasma spp. and protozoa Babesia)
- natural reservoir is the mouse (and important to tick life cycle)
- common in northeastern US
Borrelia burgdorferi
Lyme Disease Symptoms
A Key Lyme pie to the FACE:
- Facial nerve palsy (typically bilateral)
- Arthritis
- Cardiac block
- Erythema migrans
Stages of Lyme Disease
- Stage 1—Early Localized: erythema migrans (typical “bulls-eye” configuration is pathognomonic but not always present), flu‑like symptoms
- Stage 2—Early Disseminated: secondary lesions, carditis, AV block, facial nerve (Bell) palsy, migratory myalgias/transient arthritis
- Stage 3—Late Disseminated: encephalopathy, chronic arthritis
Lyme disease is treated with _____.
- Doxycycline (1st line)
- Amoxicillin
- Cefuroxime (pregnant women and children)
Bacteria:
- spirochete
- hook-shaped ends
- found in water contaminated with animal urine
Leptospira interrogans
_____ presents with flu-like symptoms, myalgias (classically of calves), jaundice, photophobia with conjunctival suffusion (erythema without exudate). Prevalent among surfers and in tropics (eg. Hawaii).
Leptospirosis
_____ is the severe form of _____ with jaundice and azotemia from liver and kidney dysfunction, fever, hemorrhage and anemia.
Weil Disease
(Icterohemorrhagic Leptospirosis)
Bacteria:
- spirochete
- causes syphilis
Treponema pallidum
Syphilis:
- localized disease presenting with painless chancre
- dark-field microscopy is used to visualize treponemes in fluid from chancre
- VDRL ⊕ in ~ 80%
Primary Syphilis
Syphilis:
- disseminated disease with constitutional symptoms
- maculopapular rash C (including palms and soles)
- condylomata lata (smooth, painless, wart-like white lesions on genitals)
- lymphadenopathy
- patchy hair loss
- confirmable with dark-field microscopy
-
Serologic Testing:
- VDRL/RPR—nonspecific
- FTA-ABS—specific, confirmatory
- latent syphilis (⊕ serology without symptoms) may follow
Secondary Syphilis
Secondary = Systemic
Syphilis:
- gummas (chronic granulomas)
- aortitis (vasa vasorum destruction)
- neurosyphilis (tabes dorsalis, “general paresis”)
- Argyll Robertson pupil (constricts with accommodation but is not reactive to light; also called “prostitute’s pupil” since it accommodates but does not react)
-
Signs:
- broad-based ataxia
- ⊕ Romberg
- Charcot joint
- stroke without hypertension
- Neurosyphilis: test spinal fluid with VDRL, FTA-ABS, and PCR.
Tertiary Syphilis
Syphilis:
- rhagades (linear scars at angle of mouth)
- snuffles (nasal discharge)
saddle nose - notched (Hutchinson) teeth
- mulberry molars
- short maxilla
- saber shins
- CN VIII deafness
Congenital Syphilis
To prevent congenital syphilis, treat the mother early in pregnancy, as placental transmission typically occurs after the _____.
1st Trimester
VDRL detects nonspecific antibody that
reacts with beef cardiolipin. Quantitative,
inexpensive, and widely available test for
syphilis (sensitive but not specific).
VDRL False Positives
False-Positive results on VDRL with:
- Pregnancy
- Viral Infection (eg. EBV, Hepatitis)
- Drugs
- Rheumatic Fever
- Lupus and Leprosy
_____ is a flu-like syndrome (fever, chills, headache, myalgia) after antibiotics are started; due to killed bacteria (usually spirochetes) releasing toxins.
Jarisch-Herxheimer Reaction
Bacteria:
- Gram-variable rod
- pleomorphic
- bacterial vaginosis
- presents as a gray vaginal discharge with a fishy smell
- nonpainful (vs. vaginitis)
- associated with sexual activity, but not sexually transmitted
- bacterial vaginosis is also characterized by overgrowth of certain anaerobic bacteria in vagina
- Clue Cells (vaginal epithelial cells covered with bacteria) have stippled appearance along outer margin
Gardnerella vaginalis
I don’t have a clue why I smell fish in the vegetable (vagina) garden!
In _____, mixing Gardnerella vaginalis discharge with 10% KOH enhances its fishy odor.
Amine Whiff Test
Gardnerella vaginalis is treated with _____.
- Metronidazole
- Clindamycin
Bacteria:
- cannot make their own ATP
- obligate intracellular organisms
- cause mucosal infections
Chlamydiae
Chlamys = cloak (intracellular)
2 Forms of Chlamydiae
-
Elementary Body
- small, dense
- “Enfectious”
- Enters cell via Endocytosis
- transforms into reticulate body
-
Reticulate Body
- Replicates in cell by fission
- Reorganizes into elementary bodies
Chlamydiae:
- reactive arthritis (Reiter syndrome)
- neonatal and follicular adult conjunctivitis
- nongonococcal urethritis
- PID
Chlamydia trachomatis
Chlamydiae:
- atypical pneumonia
- transmitted by aerosol
- Chlamydophila pneumoniae
- Chlamydophila psittaci
Chlamydiae:
- avian reservoir (parrots)
- atypical pneumonia
Chlamydophila psittaci
Chlamydia is diagnosed with _____.
PCR
Cytoplasmic inclusions (reticulate bodies) of Chlamydia are seen on _____.
- Giemsa
- Fluorescent Antibody-Stained Smear
The chlamydial cell wall lacks classic peptidoglycan (due to reduced muramic acid), rendering _____ ineffective.
β-lactam antibiotics
Chlamydia is treated with _____.
- Azithromycin (favored because of one-time treatment)
- Doxycycline (+ Ceftriaxone for possible concomitant gonorrhea)
Chlamydia trachomatis Serotypes:
- found in Africa
- cause blindness due to follicular conjunctivitis
- chronic infection
Types A, B, and C
ABC = Africa, Blindness, Chronic infection
Chlamydia trachomatis Serotypes:
- urethritis/PID
- ectopic pregnancy
- neonatal pneumonia (staccato cough) with eosinophilia
- neonatal conjunctivitis (1–2 weeks after birth)
- neonatal disease can be acquired during passage through infected birth canal
Types D–K
Chlamydia trachomatis Serotypes:
- Lymphogranuloma Venereum
- small, painless ulcers on genitals → swollen, painful inguinal lymph nodes that ulcerate (buboes)
- treated with Doxycycline
Types L1, L2, and L3
Chlamydia trachomatis causes _____ which presents with small, painless ulcers on genitals → swollen, painful inguinal lymph nodes that ulcerate (buboes)
Lymphogranuloma Venereum
_____ is infectious disease transmitted between animals and humans.
Zoonosis
Zoonotic Bacteria:
- Anaplasmosis
- Ixodes ticks (live on deer and mice)
Anaplasma spp.
Zoonotic Bacteria:
- Cat Scratch Disease
- Bacillary Angiomatosis
Bartonella spp.
Zoonotic Bacteria:
- Lyme disease
- Ixodes ticks (live on deer and mice)
Borrelia burgdorferi
Zoonotic Bacteria:
- Relapsing Fever
- louse (recurrent due to variable surfac antigens)
Borrelia recurrentis
Zoonotic Bacteria:
- Brucellosis
- Undulant Fever
- unpasteurized dairy
Brucella spp.
Zoonotic Bacteria:
- bloody diarrhea
- feces from infected pets/animals
- contaminated meats/foods/hands
Campylobacter
Zoonotic Bacteria:
- Psittacosis
- parrots, other birds
Chlamydophila psittaci
Zoonotic Bacteria:
- Q Fever
- aerosols of cattle/sheep amniotic fluid
Coxiella burnetii
Zoonotic Bacteria:
- Ehrlichiosis
- Amblyomma (lone star tick)
Ehrlichia chaffeensis
Zoonotic Bacteria:
- Tularemia
- ticks, rabbits, deer flies
Francisella tularensis
Zoonotic Bacteria:
- Leptospirosis
- animal urine in water
- recreational water use
Leptospira spp.
Zoonotic Bacteria:
- Leprosy
- lepromatous form is contagious
- armadillo (rare)
Mycobacterium leprae
Zoonotic Bacteria:
- Cellulitis
- Osteomyelitis
- animal bite, cats, dogs
Pasteurella multocida
Zoonotic Bacteria:
- epidemic typhus
- human to human via human body louse
Rickettsia prowazekii
Zoonotic Bacteria:
- Rocky Mountain Spotted Fever
- Dermacentor (dog tick)
Rickettsia rickettsii
Zoonotic Bacteria:
- endemic typhus
- fleas
Rickettsia typhi
Zoonotic Bacteria:
- diarrhea (which may be bloody)
- vomiting
- fever
- abdominal cramps
- reptiles and poultry
Salmonella spp.
(except S. typhi)
Zoonotic Bacteria:
- Plague
- fleas (rats and prairie dogs are reservoirs)
Yersinia pestis
Rickettsial diseases and vector-borne illnesses are treated with _____.
- Doxycycline (caution during pregnancy)
- Chloramphenicol (alternative)
Common Rashes:
- Rickettsia rickettsii
- vector is tick
- despite its name, disease occurs primarily in the South Atlantic states, especially North Carolina
- rash typically starts at wrists and ankles and then spreads to trunk, palms, and soles
-
Classic Triad:
- headache
- fever
- rash (vasculitis)
Rocky Mountain Spotted Fever
You drive CARS using your palms and soles.
Palms and Soles Rash:
- Coxsackievirus A Infection (Hand, Foot, and Mouth Disease)
- Rocky Mountain Spotted Fever
- 2° Syphilis.
Common Rashes:
- Endemic (fleas)—R. typhi
- Epidemic (human body louse)—R. prowazekii
- rash starts centrally and spreads out, sparing palms and soles.
Typhus
R**ickettsii on the wR**ists
Typhus on the Trunk
Rare Rashes:
- Ehrlichia
- vector is tick
- monocytes with morulae (mulberry-like inclusions) in cytoplasm
Ehrlichiosis
MEGA berry:
- Monocytes = Ehrlichiosis
- Granulocytes = Anaplasmosis
Rare Rashes:
- Anaplasma
- vector is tick
- granulocytes with morulae (mulberry-like inclusions) in cytoplasm
Anaplasmosis
MEGA berry:
- Monocytes = Ehrlichiosis
- Granulocytes = Anaplasmosis
Rare Rashes:
- Coxiella burnetii—not in the Rickettsia genus, but closely related
- no arthropod vector
- spores are inhaled as aerosols from cattle/sheep amniotic fluid
- pneumonia
- common cause of culture ⊝ endocarditis
Q fever
Q fever is Queer because it has no rash or vector and its causative organism can survive outside in its endospore form.
Bacteria:
- pleomorphic
- no cell wall
- not seen on Gram stain
- grown on Eaton agar
- classic cause of atypical “walking” pneumonia (insidious onset, headache, nonproductive cough, patchy or diffuse interstitial infiltrate)
- CXR looks worse than patient
- high titer of cold agglutinins (IgM) which can agglutinate RBCs
- bacterial membrane contains sterols for stability
- pneumonia is more common in patients < 30 years old
- frequent outbreaks in military recruits and prisons
- Mycoplasma pneumoniae*
- Mycoplasma* gets cold without a coat (cell wall).
Mycoplasma pneumoniae is treated with _____.
- Macrolides
- Doxycycline
- Fluoroquinolone
*Penicillin ineffective since Mycoplasma have no cell wall
Mycoses:
- pneumonia
- can disseminate
- caused by dimorphic fungi:
- cold (20°C) = mold
- heat (37°C) = yeast
- only exception is Coccidioides, which is a spherule (not yeast) in tissue
- can form granulomas (like TB)
- cannot be transmitted person-to-person (unlike TB)
Systemic Mycoses
Systemic mycoses are treated with ____.
- Local Infection
- Fluconazole
- Itraconazole
- Systemic Infection
- Amphotericin B
Systemic Mycoses
- Histoplasmosis
- Blastomycosis
- Coccidioidomycosis
- Paracoccidioidomycosis
Systemic Mycoses:
- Mississippi and Ohio River Valleys
- macrophage filled with mycoses (smaller than RBC)
- palatal/tongue ulcers
- splenomegaly
- bird (eg. starlings) or bat droppings
- diagnosis via urine/serum antigen
Histoplasmosis
Histo Hides (within macrophages)
Systemic Mycoses:
- Eastern and Central US
- broad-based budding (same size as RBC)
- inflammatory lung disease
- can disseminate to skin/bone
- verrucous skin lesions can simulate SCC
- forms granulomatous nodules
Blastomycosis
Blasto Buds Broadly
Systemic Mycoses:
- Southwestern US, California
- spherule (much larger than RBC) filled with endospores
- disseminates to skin/bone
- erythema nodosum (desert bumps) or multiforme
- arthralgias (desert rheumatism)
- can cause meningitis
Coccidioidomycosis
Systemic Mycoses:
- Latin America
- budding yeast with “captain’s wheel” formation (much larger than RBC)
- similar to blastomycosis
- males > females
Paracoccidioidomycosis
Paracoccidio parasails with the captain’s wheel all the way to Latin America.
Cutaneous Mycoses
- Tinea (Dermatophytes)
- Tinea Capitis
- Tinea Corporis
- Tinea Cruris
- Tinea Pedis
- Tinea Unguium
- Tinea (Pityriasis) Versicolor
Cutaneous Mycoses:
- clinical name for dermatophyte (cutaneous fungal) infections
- branching septate hyphae visible on KOH preparation with blue fungal stain
- associated with pruritus
Tinea
Dermatophytes
- Microsporum
- Trichophyton
- Epidermophyton
Tinea
- Tinea Capitis
- Tinea Corporis
- Tinea Cruris
- Tinea Pedis
- Tinea Unguium
Cutaneous Mycoses:
- occurs on head and scalp
- associated with lymphadenopathy, alopecia, and scaling
Tinea Capitis
Cutaneous Mycoses:
- occurs on torso
- characterized by erythematous scaling rings (“ringworm”) and central clearing
- can be acquired from contact with an infected cat or dog
Tinea Corporis
Cutaneous Mycoses:
- occurs in inguinal area
- often does not show the central clearing seen in tinea corporis
Tinea Cruris
Cutaneous Mycoses:
- occurs on feet
-
Three Varieties:
- Interdigital—most common
- Moccasin distribution
- Vesicular type
Tinea Pedis
Cutaneous Mycoses:
- occurs on nails
- Onychomycosis
Tinea Unguium
Cutaneous Mycoses:
- caused by Malassezia spp. (Pityrosporum spp.), a yeast-like fungus (not a dermatophyte despite being called tinea)
- degradation of lipids produces acids that damage melanocytes and cause hypopigmented, hyperpigmented, and/or pink patches
- less pruritic than dermatophytes
- can occur any time of year, but more common in summer (hot, humid weather)
- “spaghetti and meatballs” appearance on microscopy
Tinea (Pityriasis) Versicolor
Tinea (Pityriasis) Versicolor is treated with _____.
- Selenium Sulfide
- topical and/or oral antifungal medications
Opportunistic Fungal Infections
- Candida albicans
- Aspergillus fumigatus
- Cryptococcus neoformans
- Mucor spp.
- Rhizopus spp.
Opportunistic Fungal Infections:
- dimorphic
- pseudohyphae and budding yeasts at 20°C
- germ tubes a 37°C
- systemic or superficial fungal infection
- oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDS)
- vulvovaginitis (diabetes, use of antibiotics)
- diaper rash
- endocarditis (IV drug users)
- disseminated candidiasis (especially in neutropenic patients)
- chronic mucocutaneous _____
Candida albicans
Candida albicans is treated with _____.
- Vaginal
- Oral Fluconazole
- Topical Azole
- Oral/Esophageal
- Nystatin
- Fluconazole
- Echinocandins
- Systemic
- Fluconazole
- Echinocandins
- Amphotericin B
Opportunistic Fungal Infections:
- monomorphic septate hyphae
- branch at 45° acute angle
- invasive aspergillosis in immunocompromised patients and in neutrophil dysfunction (eg. chronic granulomatous disease)
- aspergillomas in pre-existing lung cavities, especially after TB infection
- some species produce Aflatoxins (associated with hepatocellular carcinoma)
Aspergillus fumigatus
Aspergillus, Acute Angle, Aflatoxins
_____ is a hypersensitivity response associated with asthma and cystic fibrosis; may cause bronchiectasis and eosinophilia.
Allergic Bronchopulmonary Aspergillosis (ABPA)
Opportunistic Fungal Infections:
- 5–10 μm with narrow budding
- heavily encapsulated yeast
- not dimorphic
- found in soil and pigeon droppings
- acquired through inhalation with hematogenous dissemination to meninges
- culture on Sabouraud agar
- highlighted with India ink (clear halo) and mucicarmine (red inner capsule)
- latex agglutination test detects polysaccharide capsular antigen and is more specific
- causes disseminated infection, meningitis, and encephalitis (“soap bubble” lesions in brain), primarily in immunocompromised
Cryptococcus neoformans
Cryptococcus neoformans is treated with _____.
Amphotericin B + Flucytosine followed by Fuconazole for cryptococcal meningitis
Opportunistic Fungal Infections:
- irregular, broad, nonseptate hyphae
- branching at wide angles
- mucormycosis mostly in ketoacidotic diabetic and/or neutropenic patients (eg. leukemia)
- inhalation of spores → fungi proliferate in blood vessel walls, penetrate cribriform plate, and enter brain
- rhinocerebral, frontal lobe abscess
- cavernous sinus thrombosis
- headache, facial pain, black necrotic eschar on face
- may have cranial nerve involvement
Mucor and Rhizopus spp.
Mucor and Rhizopus spp. are treated with _____.
- surgical debridement
- Amphotericin B
- Isavuconazole
Mycoses:
- causes _____ pneumonia (PCP), a diffuse interstitial pneumonia
- yeast-like fungus (originally classified as protozoan)
- most infections are asymptomatic
- immunosuppression (eg. AIDS) predisposes to disease
- diffuse, bilateral ground-glass opacities on CXR/CT, with pneumatoceles
- diagnosed by lung biopsy or lavage
- disc-shaped yeast seen on methenamine silver stain of lung tissue
Pneumocystis jirovecii
Pneumocystis jirovecii is treated with _____.
- TMP-SMX
- Pentamidine
- Atovaquone
- Dapsone (prophylaxis only)
- start prophylaxis when CD4+ count drops to < 200 cells/mm3 in HIV patients
Mycoses:
- Sporotrichosis
- dimorphic, cigar-shaped budding yeast that grows in branching hyphae with rosettes of conidia
- lives on vegetation
- when spores are traumatically introduced into the skin, typically by a thorn (“rose gardener’s disease”), causes local pustule or ulcer with nodules along draining lymphatics (ascending lymphangitis)
- disseminated disease possible in immunocompromised host
Sporothrix schenckii
A rose gardener smokes cigars and pot.
Sporothrix schenckii is treated with _____.
- Itraconazole
- Potassium Iodide
A rose gardener smokes cigars and pot.
Protozoa:
Gastrointestinal Infections
- Giardia lamblia
- Entamoeba histolytica
- Cryptosporidium
Protozoa:
- bloating, flatulence, foul-smelling, fatty diarrhea
- (often seen in campers/hikers)
- transmitted through cysts in water
- diagnosed with multinucleated trophozoites/cysts in stool or antigen detection
Giardia lamblia
fatty stools of Giardia = fat-rich Ghirardelli chocolates
_____ causes bloating, flatulence, and foul-smelling, fatty diarrhea (often seen in campers/hikers).
Giardiasis
fatty stools of Giardia = fat-rich Ghirardelli chocolates
Giardia lamblia is treated with _____.
Metronidazole
Protozoa:
- bloody diarrhea (dysentery)
- liver abscess (“anchovy paste” exudate)
- RUQ pain
- histology of colon biopsy shows flask-shaped ulcers
- transmitted through cysts in water
- diagnosed with serology, antigen testing, and/or trophozoites (with engulfed RBCs in the cytoplasm) or cysts with up to 4 nuclei in stool
Entamoeba histolytica
Entamoeba Eats Erythrocytes
_____ causes bloody diarrhea (dysentery), liver abscess (“anchovy paste” exudate), and RUQ pain. Histology of colon biopsy shows flask-shaped ulcers.
Amebiasis
Entamoeba histolytica is treated with _____.
- Metronidazole
- Paromomycin—asymptomatic cyst passers
- Iodoquinol—asymptomatic cyst passers
Protozoa:
- severe diarrhea in AIDS
- mild disease (watery diarrhea) in immunocompetent hosts
- transmitted through oocysts in water
- diagnosed with oocysts on acid-fast stain or antigen detection
Cryptosporidium
Cryptosporidium is treated with _____.
- Nitazoxanide—immunocompetent hosts
- prevention—filtering city water supplies
Protozoa:
CNS Infections
- Toxoplasma gondii
- Naegleria fowleri
- Trypanosoma brucei
Protozoa:
- Imononucleosis-like symptoms
- ⊝ heterophile antibody test
- reactivation in AIDS → brain abscesses usually seen as multiple ring-enhancing lesions on MRI
- congenital infection prests with the classic triad of chorioretinitis, hydrocephalus, and intracranial calcifications
- transmitted through cysts in meat (most common) or oocysts in cat feces
- crosses the placenta (pregnant women should avoid cats)
- diagnosed with serology or biopsy (tachyzoite)
Toxoplasma gondii
Toxoplasma gondii is treated with _____.
Sulfadiazine + Pyrimethamine
Protozoa:
- rapidly fatal meningoencephalitis
- swimming in warm freshwater ↑ risk
- enters via cribriform plate
- diagnosed with amoebas in CSF
Naegleria fowleri
A Nalgene bottle is filled with fresh water.
Naegleria fowleri is treated with _____.
Amphotericin B—has been effective for a few survivors
Protozoa:
- enlarged lymph nodes
- recurring fever (due to antigenic variation)
- somnolence
- coma
- transmitted through the Tsetse fly—painful bite
- diagnosed with trypomastigote in blood smear
Trypanosoma brucei
Trypanosoma brucei causes _____ which presents with enlarged lymph nodes, recurring fever (due to antigenic variation), somnolence, and coma.
African Sleeping Sickness
Trypanosoma brucei is treated with _____.
- Suramin—bloodborne disease
- Melarsoprol—CNS penetration
I sure am mellow when I’m sleeping.
Protozoa:
Hematologic Infections
-
Plasmodium
- P. vivax
- P. ovale
- P. falciparum
- P. malariae
- Babesia
Protozoa:
- Malaria—fever, headache, anemia, splenomegaly
- transmitted through the Anopheles mosquito
- diagnosed with blood smear
- trophozoite ring form within RBC
- schizont containing merozoites
Plasmodium
Plasmodium:
- 48-hr cycle (tertian; includes fever on first day and third day, thus fevers are actually 48 hr apart)
- dormant form (hypnozoite) in liver
- red granules (Schüffner stippling) throughout RBC cytoplasm
P. vivax/ovale
Plasmodium:
- severe
- irregular fever patterns
- parasitized RBCs occlude capillaries in brain (cerebral malaria), kidneys, and lungs
P. falciparum
Plasmodium:
72-hr cycle (quartan)
P. malariae
Plasmodium is treated with _____.
- Sensitive Species
- Chloroquine—blocks Plasmodium heme polymerase
- Resistant Species
- Mefloquine
- Atovaquone/Proguanil
- Life-Threatening
- IV Quinidine
- IV Artesunate—test for G6PD deficiency
- For P. vivax/ovale
- add Primaquine for hypnozoite—test for G6PD deficiency
Protozoa:
- fever and hemolytic anemia
- predominantly in northeastern US
- asplenia ↑ risk of severe disease
- transmitted through the Ixodes tick (same as Borrelia burgdorferi of Lyme disease; may often coinfect humans)
- diagnosed with blood smear or PCR
- ring form
- “Maltese cross”
Babesia
Babesia is treated with _____.
Atovaquone + Azithromycin
Protozoa:
Visceral Infections
- Trypanosoma cruzi
- Leishmania donovani
Protozoa:
- Chagas disease—dilated cardiomyopathy with apical atrophy, megacolon, megaesophagus
- predominantly in South America
- unilateral periorbital swelling (Romaña sign) characteristic of acute stage
- transmitted through the Triatomine (“kissing”) bug, a type of reduviid bug, deposits feces in a painless bite (much like a kiss)
- diagnosed with Trypomastigote in blood smear
Trypanosoma cruzi
Trypanosoma cruzi is treated with _____.
- Benznidazole
- Nifurtimox
I’m cruzing in my Benz, with a fur coat on.
Protozoa:
- Visceral (kala-azar)—spiking fevers, hepatosplenomegaly, pancytopenia
- Cutaneous—skin ulcers
- transmitted through the sandfly
- macrophages containing amastigotes
Leishmania donovani
Leishmania donovani is treated with _____.
- Amphotericin B
- Sodium Stibogluconate
Protozoa:
Sexually Transmitted Infections
Trichomonas vaginalis
Protozoa:
- Vaginitis—foul-smelling greenish discharge, itching and burning
- transmitted through sexual contact (cannot exist outside human because it cannot form cysts)
- diagnosed with trophozoites (motile) on wet mount
- “strawberry cervix”
Trichomonas vaginalis
Trichomonas vaginalis is treated with _____.
Metronidazole for patient and partner (prophylaxis)
Nematodes (Roundworms):
Ingested
You’ll get sick if you EATTT these!
- Enterobius
- Ascaris
- Toxocara
- Trichinella
- Trichuris
Nematodes (Roundworms):
Cutaneous
These get into your feet from the SANd.
- Strongyloides
- Ancylostoma
- Necator
Nematodes (Roundworms):
Bites
Lay LOW to avoid getting bitten.
- Loa loa
- Onchocerca volvulus
- Wuchereria bancrofti
Nematodes (Roundworms):
Intestinal
- Enterobius vermicularis (pinworm)
- Ascaris lumbricoides (giant roundworm)
- Strongyloides stercoralis (threadworm)
- Ancylostoma duodenale (hookworms)
- Necator americanus (hookworms)
- Trichinella spiralis
- Trichuris trichiura (whipworm)
Nematodes (Roundworms):
- causes anal pruritus
- diagnosed by seeing egg via the tape test
- fecal-oral route
Enterobius vermicularis (pinworm)
Enterobius vermicularis (pinworm) is treated with _____.
- Pyrantel Pamoate
- Bendazoles
Nematodes (Roundworms):
- may cause obstruction at ileocecal valve, biliary obstruction, and intestinal perforation
- migrates from nose/mouth
- fecal-oral route
- knobby-coated, oval eggs seen in feces under microscope
Ascaris lumbricoides (giant roundworm)
Ascaris lumbricoides (giant roundworm) is treated with _____.
Bendazoles
Nematodes (Roundworms):
- Autoinfection—rarely, some larvae may penetrate the intestinal wall to enter the bloodstream without leaving the body
- larvae in soil penetrate skin
- rhabditiform larvae seen in feces under microscope
Strongyloides stercoralis (threadworm)
Strongyloides stercoralis (threadworm) is treated with _____.
- Ivermectin
- Bendazoles
Nematodes (Roundworms):
- Cutaneous Larva Migrans—pruritic, serpiginous rash from walking barefoot on contaminated beach
- cause anemia by sucking blood from intestinal wall
- larvae penetrate skin
- Ancylostoma duodenale
- Necator americanus
*hookworms
Ancylostoma duodenale and Necator americanus (hookworms) are treated with _____.
- Bendazoles
- Pyrantel Pamoate
Nematodes (Roundworms):
- larvae enter bloodstream, encyst in striated muscle → muscle inflammation
- causes fever, vomiting, nausea, periorbital edema, and myalgia
- undercooked meat (especially pork)
- fecal-oral (less likely)
Trichinella spiralis
Trichinella spiralis is treated with _____.
Bendazoles
Nematodes (Roundworms):
- often asymptomatic
- loose stools
- anemia
- rectal prolapse in children (heavy infection)
- fecal-oral route
Trichuris trichiura (whipworm)
Trichuris trichiura (whipworm) is treated with _____.
Bendazoles
Nematodes (Roundworms):
Tissue
- Toxocara canis
- Onchocerca volvulus
- Loa loa
- Wuchereria bancrofti
Nematodes (Roundworms):
- Visceral Larva Migrans—nematode migrate to blood through intestinal wall → inflammation and damage
- often affects heart (myocarditis), liver, eyes (visual impairment, blindness), and CNS (seizures, coma)
- fecal-oral route
Toxocara canis
Toxocara canis is treated with _____.
Bendazoles
Nematodes (Roundworms):
- skin changes, loss of elastic fibers, and river blindness (black flies, black skin nodules, “black sight”)
- allergic reaction to microfilaria possible
- transmitted through the female blackfly
Onchocerca volvulus
Onchocerca volvulus is treated with _____.
Ivermectin
Ivermectin for River Blindness
Nematodes (Roundworms):
- swelling in ski
- worm in conjunctiva
- transmitted through the deer fly, horse fly, and mango fly
Loa loa
Loa loa is treated with _____.
Diethylcarbamazine
Nematodes (Roundworms):
- Lymphatic Filariasis (Elephantiasis)—worms invade lymph nodes → inflammation → lymphedema
- symptom onset after 9 mo.–1 yr.
- transmitted through the female mosquito
Wuchereria bancrofti
Wuchereria bancrofti is treated with _____.
Diethylcarbamazine
Cestodes (Tapeworms)
- Taenia solium
- Diphyllobothrium latum
- Echinococcus granulosus
Cestodes (Tapeworms):
- Intestinal Tapeworm—ingestion of larvae encysted in undercooked pork
- Cysticercosis
- Neurocysticercosis (cystic CNS lesions, seizures)
- ingestion of eggs in food contaminated with human feces
Taenia solium
Taenia solium is treated with _____.
- Praziquantel
- Albendazole for neurocysticercosis
Cestodes (Tapeworms):
- Vitamin B12 deficiency (tapeworm competes for B12 in intestine) → megaloblastic anemia
- ingestion of larvae in raw freshwater fish
Diphyllobothrium latum
Diphyllobothrium latum is treated with _____.
Praziquantel
Cestodes (Tapeworms):
- Hydatid cysts (“eggshell calcification”) in liver
- cyst rupture can cause anaphylaxis
- ingestion of eggs in food contaminated with dog feces
- sheep are an intermediate host
Echinococcus granulosus
Echinococcus granulosus is treated with _____.
Albendazole
Trematodes (Flukes)
- Schistosoma
- Clonorchis sinensis
Trematodes (Flukes):
-
S. mansoni
- egg with lateral spine
- liver and spleen enlargement fibrosis, inflammation, portal hypertension
-
S. haematobium
- chronic infection
- egg with terminal spine
- can lead to squamous cell carcinoma of the bladder (painless hematuria) and pulmonary hypertension
- snails are intermediate host cercariae penetrate skin of humans in contact with contaminated fresh water (eg. swimming or bathing)
Schistosoma
Trematodes (Flukes):
- egg with lateral spine
- liver and spleen enlargement, fibrosis, inflammation, and portal hypertension
Schistosoma mansoni
Trematodes (Flukes):
- chronic infection
- egg with terminal spine
- can lead to squamous cell carcinoma of the bladder (painless hematuria) and pulmonary hypertension
Schistosoma haematobium
Schistosoma is treated with _____.
Praziquantel
Cestodes (Tapeworms):
- biliary tract inflammation → pigmented gallstones
- associated with cholangiocarcinoma
- undercooked fish
Clonorchis sinensis
Clonorchis sinensis is treated with _____.
Praziquantel
Ectoparasites
- Sarcoptes scabiei
- Pediculus humanus
- Phthirus pubis
Ectoparasites:
- mites burrow into stratum corneum—pruritus (worse at night) and serpiginous burrows (lines) in webspace of hands and feet
- common in children, crowded populations (jails, nursing homes)
- transmission through skin-to-skin contact (most common) or via fomites
Sarcoptes scabiei
Sarcoptes scabiei is treated with _____.
- Permethrin cream
- washing/drying all clothing/bedding
- treat close contacts
Ectoparasites:
- blood-sucking lice that cause intense pruritus with associated excoriations, commonly on scalp and neck (head lice) or waistband and axilla (body lice)
- can transmit Rickettsia prowazekii (epidemic typhus), Borrelia recurrentis (relapsing fever), Bartonella quintana (trench fever).
- Pediculus humanus
- Phthirus pubis
Pediculus humanus and Phthirus pubis are treated with _____.
- Pyrethroids
- Malathion
- Ivermectin lotion
- nit combing
*children with head lice can be treated at home without interrupting school attendance
Parasites:
- biliary tract disease
- cholangiocarcinoma
Clonorchis sinensis
Parasites:
Neurocysticercosis—brain cysts, seizures
Taenia solium
Parasites:
- hematuria
- squamous cell bladder cancer
Schistosoma haematobium
Parasites:
liver (hydatid) cysts
Echinococcus granulosus
Parasites:
microcytic anemia
- Ancylostoma
- Necator
Parasites:
- myalgias
- periorbital edema
Trichinella spiralis
Parasites:
perianal pruritus
Enterobius
Parasites:
portal hypertension
- Schistosoma mansoni
- Schistosoma japonicum
Parasites:
Vitamin B12 Deficiency
Diphyllobothrium latum
Viral Structure
Viral Genetics:
exchange of genes between 2 chromosomes by crossing over within regions of significant base sequence homology
Recombination
Viral Genetics:
- when viruses with segmented genomes (eg. influenza virus) exchange genetic material
- the 2009 novel H1N1 influenza A pandemic emerged via complex viral reassortment of genes from human, swine, and avian viruses
- has potential to cause antigenic shift.
Reassortment
Viral Genetics:
- when 1 of 2 viruses that infect the cell has a mutation that results in a nonfunctional protein, the nonmutated virus “complements” the mutated one by making a functional protein that serves both viruses
- hepatitis D virus requires the presence of replicating hepatitis B virus to supply HBsAg, the envelope protein for HDV
Complementation
Viral Genetics:
- occurs with simultaneous infection of a cell with 2 viruses
- genome of virus A can be partially or completely coated (forming pseudovirion) with the surface proteins of virus B
- type B protein coat determines the tropism (infectivity) of the hybrid virus
- the progeny from this infection have a type A coat that is encoded by its type A genetic material
Phenotypic Mixing
All DNA viruses have dsDNA genomes except _____.
Parvoviridae (ssDNA)
All are dsDNA (like our cells), except “part-of-a-virus” (parvovirus) is ssDNA.
Parvus = small
All DNA viruses are linear except _____.
Circular
- Papillomaviruses—supercoiled
- Polyomaviruses—supercoiled
- Hepadnaviruses—incomplete
All RNA viruses have ssRNA genomes except _____.
Reoviridae (dsRNA)
All are ssRNA, except “repeato-virus” (reovirus) is dsRNA.
⊕ Stranded RNA Viruses
- Retrovirus
- Togavirus
- Flavivirus
- Coronavirus
- Hepevirus
- Calicivirus
- Picornavirus
I went to a retro toga party, where I drank flavored Corona and ate hippie California pickles.
Naked Viral Genome Infectivity:
Purified nucleic acids of most dsDNA (except poxviruses and HBV) and ⊕ strand ssRNA (≈ mRNA) viruses are _____.
infectious
Naked Viral Genome Infectivity:
Naked nucleic acids of ⊝ strand ssRNA and dsRNA viruses are _____.
not infectious
Naked Viral Genome Infectivity:
Naked nucleic acids of ⊝ strand ssRNA and dsRNA viruses are not infectious. They require _____ contained in the complete virion.
polymerases
Generally, enveloped viruses acquire their envelopes from the _____ when they exit from cell.
plasma membrane
Generally, enveloped viruses acquire their envelopes from plasma membrane when they exit from cell. Exceptions include herpesviruses, which acquire envelopes from the _____.
nuclear membrane
Naked (Nonenveloped) Viruses
- Papillomavirus
- Adenovirus
- Parvovirus
- Polyomavirus
- Calicivirus
- Picornavirus
- Reovirus
- Hepevirus
DNA = PAPP; RNA = CPR and hepevirus.
Give PAPP smears and CPR to a naked hippie.
DNA Viruses
HHAPPPPy Viruses:
- Hepadna
- Herpes
- Adeno
- Pox
- Parvo
- Papilloma
- Polyoma
DNA viruses are icosahedral except _____.
Pox (complex)
DNA viruses replicate in the nucleus except _____.
Pox
- carries own DNA-dependent RNA polymerase
Pox is out of the box (nucleus).
DNA Viruses:
- ⊕ envelope
- DS
- linear
Herpesviruses
DNA Viruses:
- ⊕ envelope
- DS
- linear
- largest DNA virus
- Molluscum Contagiosum—flesh-colored papule with central umbilication
Poxvirus
_____ was eradicated worldwide by use of the live-attenuated vaccine.
Smallpox
_____ presents with “milkmaid blisters”.
Cowpox
DNA Viruses:
- ⊕ envelope
- partially DS
- circular
- HBV
- acute or chronic hepatitis
- not a retrovirus but has reverse transcriptase
Hepadnavirus
DNA Viruses:
- ⊝ envelope
- DS
- linear
- febrile pharyngitis—sore throat
- acute hemorrhagic cystitis
- pneumonia
- conjunctivitis—“pink eye”
- gastroenteritis
Adenovirus
DNA Viruses:
- ⊝ envelope
- DS
- circular
- HPV
- warts—serotypes 1, 2, 6, 11
- CIN, cervical cancer—most commonly 16, 18
Papillomavirus
DNA Viruses:
- ⊝ envelope
- DS
- circular
- JC virus—progressive multifocal leukoencephalopathy (PML) in HIV
- BK virus—transplant patients, commonly targets kidney
Polyomavirus
JC: Junky Cerebrum
BK: Bad Kidney
DNA Viruses:
- ⊝ envelope
- SS
- linear
- smallest DNA virus
- B19 virus
- aplastic crises in sickle cell disease
- “slapped cheek” rash in children (erythema infectiosum, or fifth disease)
- RBC destruction in fetus leads to hydrops fetalis and death
- in adults it leads to pure RBC aplasia and rheumatoid arthritis-like symptoms
Parvovirus
Herpesviruses:
- transmitted through respiratory secretions and saliva
- gingivostomatitis
- keratoconjunctivitis
- herpes labialis
- herpetic whitlow on finger
- temporal lobe encephalitis
- esophagitis
- erythema multiforme
- most commonly latent in trigeminal ganglia
- most common cause of sporadic encephalitis; can present as altered mental status, seizures, and/or aphasia
Herpes Simplex Virus-1
Herpesviruses:
- transmitted through sexual contact, perinatal
- herpes genitalis
- neonatal herpes
- most commonly latent in sacral ganglia
- viral meningitis is more common
Herpes Simplex Virus-2
Herpesviruses:
- transmitted through respiratory secretions
- encephalitis
- pneumonia
- latent in dorsal root or trigeminal ganglia
- CN V1 branch involvement can cause Herpes Zoster Ophthalmicus
Varicella-Zoster Virus (HHV-3)
Herpesviruses:
- transmitted through respiratory secretions and saliva
- “kissing disease”(common in teens, young adults)
- Mononucleosis
- fever, hepatosplenomegaly, pharyngitis, and lymphadenopathy (especially posterior cervical nodes)
- avoid contact sports until resolution due to risk of splenic rupture
- associated with lymphomas (eg. endemic Burkitt lymphoma), nasopharyngeal carcinoma (especially Asian adults), and lymphoproliferative disease in transplant patients.
- infects B cells through CD21
- atypical lymphocytes on peripheral blood smear G—not infected B cells but reactive cytotoxic T cells
- ⊕ Monospot Test—heterophile antibodies detected by agglutination of sheep or horse RBCs
- use of amoxicillin in mononucleosis can cause characteristic maculopapular rash
Epstein-Barr Virus (HHV-4)
Herpesviruses:
- transmitted through congenital transfusion,
- sexual contact, saliva, urine, and transplant
- Mononucleosis (⊝ Monospot) in immunocompetent patients
- infection in immunocompromised, especially pneumonia in transplant patients
- esophagitis
- AIDS retinitis (“sightomegalovirus”)
- hemorrhage
- cotton-wool exudates
- vision loss
- infected cells have characteristic “owl eye” intranuclear inclusions
- latent in mononuclear cells
Cytomegalovirus (HHV-5)
AIDS retinitis = “sightomegalovirus”
Herpesviruses:
- transmitted through saliva
- Roseola Infantum (Exanthem Subitum)
- high fevers for several days that can cause seizures
- followed by diffuse macular rash
- Roseola
- fever first
- rosy (rash) later
Human Herpesviruses 6 and 7
HHV-7—less common cause of Roseola
Herpesviruses:
- transmitted through sexual contact
- Kaposi sarcoma (neoplasm of endothelial cells)
- seen in HIV/AIDS and transplant patients
- dark/violaceous plaques or nodules representing vascular proliferations
- can also affect GI tract and lungs
Human Herpesvirus 8
HSV Identification:
- skin
- genitalia
Viral Culture
HSV Identification:
Herpes Encephalitis
CSF PCR
HSV Identification:
skin lesions
PCR
HSV Identification:
a smear of an opened skin vesicle is used to detect multinucleated giant cells commonly seen in HSV-1, HSV-2, and VZV infection
Tzanck Test
Tzanck heavens I do not have herpes.
HSV Identification:
seen with HSV-1, HSV-2, VZV
Intranuclear Eosinophilic Cowdry Inclusions
Receptors:
CMV
Integrins (Heparan Sulfate)
Receptors:
EBV
CD21
Receptors:
HIV
- CD4
- CXCR4
- CCR5
Receptors:
Parvovirus B19
P antigen on RBCs
Receptors:
Rabies
Nicotinic AChR
Receptors:
Rhinovirus
ICAM-1
All RNA viruses replicate in the cytoplasm except _____.
- Retrovirus
- Influenza Virus
Retro flu is outta cyt (sight).
_____ are viruses that are arthropod borne (mosquitoes, ticks).
Arbovirus
Arboviruses
- Coltivirus
- Yellow Fever
- Dengue
- St. Louis Encephalitis
- West Nile Virus
- Zika Virus
- Western and Eastern Equine Encephalitis
- Chikungunya Virus
- California Encephalitis
- Sandfly Fever
- Rift Valley Fever
- Crimean-Congo Hemorrhagic Fever
RNA Viruses:
- ⊝ envelope
- DS
- linear
- 10–12 segments of RNA
- icosahedral (double) capsid
- Coltivirus—Colorado tick fever
- Rotavirus—cause of fatal diarrhea in children
Reoviruses
RNA Viruses:
- ⊝ envelope
- SS
- ⊕ linear
- icosahedral capsid
- Poliovirus—polio-Salk/Sabin vaccines—IPV/OPV
- Echovirus—aseptic meningitis
- Rhinovirus—“common cold”
- Coxsackievirus—aseptic meningitis; herpangina (mouth blisters, fever); hand, foot, and mouth disease; myocarditis; pericarditis
- HAV—acute viral hepatitis
Picornaviruses
PERCH
- Poliovirus
- Echovirus
- Rhinovirus
- Coxsackievirus
- HAV
RNA Viruses:
- ⊝ envelope
- SS
- ⊕ linear
- icosahedral capsid
- HEV
Hepevirus
RNA Viruses:
- ⊝ envelope
- SS
- ⊕ linear
- icosahedral capsid
- Norovirus—viral gastroenteritis
Caliciviruses
RNA Viruses:
- ⊕ envelope
- SS
- ⊕ linear
- icosahedral capsid
- HCV
- Yellow Fever
- Dengue
- St. Louis Encephalitis
- West Nile Virus—meningoencephalitis
- Zika Virus
Flaviviruses
RNA Viruses:
- ⊕ envelope
- SS
- ⊕ linear
- icosahedral capsid
- Rubella
- Western and Eastern Equine Encephalitis
- Chikungunya Virus
Togaviruses
RNA Viruses:
- ⊕ envelope
- SS
- ⊕ linear
- 2 copies of RNA
- icosahedral capsid (HTLV)
- complex and conical capsid (HIV)
- have reverse transcriptase
- HTLV—T-Cell Leukemia
- HIV—AIDS
Retroviruses
RNA Viruses:
- ⊕ envelope
- SS
- ⊕ linear
- helical capsid
- “common cold”
- SARS
- MERS
Coronaviruses
RNA Viruses:
- ⊕ envelope
- SS
- ⊝ linear
- 8 segments of RNA
- helical capsid
- Influenza Virus
Orthomyxoviruses
RNA Viruses:
- ⊕ envelope
- SS
- ⊝ linear
- nonsegmented RNA
- helical capsid
- Parainfluenza—croup
- RSV—bronchiolitis in babies
- Measles
- Mumps
Paramyxoviruses
PaRaMyxovirus:
- Parainfluenza
- RSV
- Measles
- Mumps
RNA Viruses:
- ⊕ envelope
- SS
- ⊝ linear
- helical capsid
- Rabies
Rhabdoviruses
RNA Viruses:
- ⊕ envelope
- SS
- ⊝ linear
- helical capsid
- Ebola/Marburg Hemorrhagic Fever—often fatal
Filoviruses
RNA Viruses:
- ⊕ envelope
- SS
- ⊕ and ⊝ circular
- 2 segments of RNA
- helical capsid
- LCMV—Lymphocytic Choriomeningitis Virus
- Lassa Fever Encephalitis—spread by rodents
Arenaviruses
RNA Viruses:
- ⊕ envelope
- SS
- ⊝ circular
- 3 segments of RNA
- helical capsid
- California Encephalitis
- Sandfly/Rift Valley Fevers
- Crimean-Congo Hemorrhagic Fever
- Hantavirus—hemorrhagic fever, pneumonia
Bunyaviruses
RNA Viruses:
- ⊕ envelope
- SS
- ⊝ circular
- uncertain capsid shape
- HDV is a “defective” virus that requires the
- presence of HBV to replicate
Delta Virus
_____ must transcribe ⊝ RNA strand to ⊕. Virion brings its own RNA-dependent RNA polymerase.
Negative-Stranded Viruses
Negative-Stranded Viruses
Always Bring Polymerase Or Fail Replication.
- Arenaviruses
- Bunyaviruses
- Paramyxoviruses
- Orthomyxoviruses
- Filoviruses
- Rhabdoviruses.
Segmented Viruses are all _____.
RNA Viruses
Segmented Viruses
BOAR
- Bunyaviruses
- Orthomyxoviruses
- Arenaviruses
- Reoviruses
_____ RNA is translated into 1 large polypeptide that is cleaved by proteases into functional viral proteins.
Picornavirus
PicoRNAvirus = small RNA virus
Picornaviruses can cause aseptic (viral) meningitis except _____.
- Rhinovirus
- HAV
Picornaviruses are all enteroviruses except _____.
- Rhinovirus
- HAV
Picornaviruses
PERCH on a “peak” (pico).
- Poliovirus
- Echovirus
- Rhinovirus
- Coxsackievirus
- HAV
Viruses:
- Picornavirus
- nonenveloped RNA virus
- cause of common cold
- > 100 serologic types
- acid labile—destroyed by stomach acid
- does not infect the GI tract (unlike the other picornaviruses)
Rhinovirus
Rhino has a runny nose.
Viruses:
- Flavivirus (also an arbovirus)
- transmitted by Aedes mosquitoes
- monkey or human reservoir
- causes high fever, black vomitus, and jaundice
- Councilman Bodies (eosinophilic apoptotic globules) on liver biopsy
Yellow Fever Virus
Flavi = yellow, jaundice
Viruses:
- Reovirus
- segmented dsRNA virus
- most important global cause of infantile gastroenteritis
- major cause of acute diarrhea in the US during winter, especially in day care centers, kindergartens
- villous destruction with atrophy leads to ↓ absorption of Na+ and loss of K+
- CDC recommends routine vaccination of all infants except those with a history of intussusception or SCID
Rotavirus
ROTAvirus = Right Out The Anus
Viruses:
- Orthomyxoviruses
- enveloped, ⊝ ssRNA viruses with 8-segment genome
- contain hemagglutinin (binds sialic acid and promotes viral entry) and neuraminidase (promotes progeny virion release) antigens
- patients at risk for fatal bacterial superinfection, most commonly S. aureus, S. pneumoniae, and H. influenzae
Influenza Viruses
Reformulated Influenza vaccine (“the flu shot”) contains viral strains most likely to appear during the flu season, due to the virus’ _____.
rapid genetic change
_____ Influenza vaccine is most frequently used.
Killed
_____ Influenza vaccine contains temperature-sensitive mutant that replicates in the nose but not in the lung; administered intranasally.
Live Attenuated
Influenza Viruses:
- causes pandemics
- reassortment of viral genome segments, such as when segments of human flu A virus reassort with swine flu A virus
Genetic/Antigenic Shift
Sudden shift is more deadly than gradual drift.
Influenza Viruses:
- causes epidemics
- minor changes based on random mutation in hemagglutinin or neuraminidase genes
Genetic/Antigenic Drift
Sudden shift is more deadly than gradual drift.
Viruses:
- Togavirus
- causes German (3-day) Measles
- causes fever, postauricular and other lymphadenopathy, arthralgias, and fine, maculopapular rash that starts on face and spreads centrifugally to involve trunk and extremities
- causes mild disease in children but serious congenital disease (a ToRCHeS infection)
- congenital infection presents with “blueberry muffin” appearance due to dermal extramedullary hematopoiesis
Rubella Virus
Viruses:
- cause disease in children
- include those that cause parainfluenza (croup), mumps, measles, RSV, and human metapneumovirus, which causes respiratory tract infection (bronchiolitis, pneumonia) in infants
- all contain surface F (fusion) protein, which causes respiratory epithelial cells to fuse and form multinucleated cells
Paramyxoviruses
_____, monoclonal antibody against F protein, prevents pneumonia caused by RSV infection in premature infants.
Palivizumab
Palivizumab for Paramyxovirus (RSV) Prophylaxis in Preemies.
Viruses:
- Paramyxoviruses
- causes Croup (Acute Laryngotracheobronchitis)
- virus membrane contains hemagglutinin (binds sialic acid and promotes viral entry) and neuraminidase (promotes progeny virion release) antigens
- results in a “seal-like” barking cough and inspiratory stridor
- narrowing of upper trachea and subglottis leads to characteristic steeple sign on x-ray
- severe Croup can result in pulsus paradoxus 2° to upper airway obstruction
Parainfluenza Viruses
Viruses:
- Paramyxovirus
- usual presentation involves prodromal fever with cough, coryza, and conjunctivitis, then eventually Koplik spots (bright red spots with blue-white center on buccal mucosa), followed 1–2 days later by a maculopapular rash that starts at the head/neck and spreads downward
- lymphadenitis with Warthin-Finkeldey giant cells (fused lymphocytes) in a background of paracortical hyperplasia
Measles (Rubeola) Virus
3 C’s of Measles:
- Cough
- Coryza
- Conjunctivitis
Sequelae of Measles
- SSPE
- Subacute Sclerosing Panencephalitis
- occurring years later
- Encephalitis
- 1:2000
- Giant Cell Pneumonia
- rare except in immunosuppressed
_____ supplementation can reduce morbidity and mortality from measles, particularly in malnourished children.
Vitamin A
Viruses:
- Paramyxovirus
- uncommon due to effectiveness of MMR vaccine
- causes parotitis, orchitis (inflammation of testes), aseptic meningitis, and pancreatitis.
- can cause sterility (especially after puberty).
Mumps Virus
Mumps makes your parotid glands and testes as
big as POM-Poms.
- Parotitis
- Orchitis
- aseptic Meningitis
- Pancreatitis
Viruses:
- bullet-shaped virus
- Negri bodies (cytoplasmic inclusions) commonly found in Purkinje cells of cerebellum and in hippocampal neurons
- has long incubation period (weeks to months) before symptom onset
- Postexposure prophylaxis is wound cleaning plus immunization with killed vaccine and rabies immunoglobulin
- example of passive-active immunity
Rabies Virus
Viruses:
- travels to the CNS by migrating in a retrograde fashion (via dynein motors) up nerve axons after binding to ACh receptors
-
Progression of Disease:
- fever, malaise → agitation, photophobia, hydrophobia, hypersalivation → paralysis, coma → death
- infection more commonly from bat, raccoon, and skunk bites than from dog bites in the US
- aerosol transmission (eg. bat caves) also possible
Rabies Virus
Viruses:
- Filovirus
- targets endothelial cells, phagocytes, and hepatocytes
- following an incubation period of up to 21 days, presents with abrupt onset of flu-like symptoms, diarrhea/vomiting, high fever, and myalgia.
- can progress to DIC, diffuse hemorrhage, shock
- diagnosed with RT-PCR within 48 hr of symptom onset
- high mortality rate
Ebola Virus
Viruses:
- Filovirus
- targets endothelial cells, phagocytes, and hepatocytes
- transmission requires direct contact with bodily fluids, fomites (including dead bodies), and infected bats or primates (apes/monkeys)
- high incidence of nosocomial infection
- supportive care, no definitive treatment
- strict isolation of infected individuals and barrier practices for health care workers are key to preventing transmission
Ebola Virus
Viruses:
- Flavivirus
- most commonly transmitted by Aedes mosquito bites
- causes conjunctivitis, low-grade pyrexia, and itchy rash in 20% of cases
- can lead to congenital microcephaly or miscarriage if transmitted in utero
- diagnose with RT-PCR or serology
- sexual and vertical transmission possible
- outbreaks more common in tropical and subtropical climates
- supportive care, no definitive treatment
Zika Virus
Viruses:
- episodes of fever and jaundice
- ↑ ALT and AST
Hepatitis Viruses
Naked viruses (HAV and HEV) lack an envelope and are not destroyed by the _____.
gut
HAV, HEV = The vowels hit your bowels.
HBV DNA Polymerase
- HBV DNA polymerase has DNA- and RNA-dependent activities.
- Upon entry into nucleus, the polymerase completes the partial dsDNA.
- Host RNA polymerase transcribes mRNA from viral DNA to make viral proteins.
- The DNA polymerase then reverse transcribes viral RNA to DNA, which is the genome of the progeny virus.
HCV lacks _____ activity → no proofreading ability → variation in antigenic structures of HCV envelope proteins. Host antibody production lags behind production of new mutant strains of HCV.
3′-5′ Exonuclease
Hepatitis Viruses:
- RNA Picornavirus
- fecal-oral route (shellfish, travelers, day care)
- Incubation Period—short (weeks)
- asymptomatic (usually), acute
- good prognosis
- no risk for HCC
- Liver Biopsy:
- hepatocyte swelling
- monocyte infiltration
- Councilman bodies
- no carrier state
HAV
Asymptomatic, Acute, Alone
Hepatitis Viruses:
- DNA Hepadnavirus
- parenteral, sexual, and perinatal transmission
- Incubation Period—long (months)
- initially like serum sickness (fever, arthralgias, rash)
- may progress to carcinoma
- risk for HCC
- adults → mostly full resolution
- neonates → worse prognosis
- Liver Biopsy:
- granular eosinophilic “ground glass” appearance
- cytotoxic T cells mediate damage
- carrier state common
HBV
Blood, Babymaking, Birthing
Hepatitis Viruses:
- RNA Flavivirus
- transmitted through blood (IVDU, post-transfusion)
- Incubation Period—long
- may progress to cirrhosis or carcinoma
- risk for HCC
- majority develop stable, chronic hepatitis C
- Liver Biopsy:
- lymphoid aggregates with focal areas of macrovesicular steatosis
- carrier state very common
HCV
Cirrhosis, Carcinoma, Chronic, Carrier
Hepatitis Viruses:
- RNA Deltavirus
- parenteral, sexual, and perinatal transmission
- Superinfection (HDV after HBV) = short
- Coinfection (HDV with HBV) = long
- initially like serum sickness (fever, arthralgias, rash)
- may progress to carcinoma
- risk for HCC
- Superinfection → worse prognosis
- Liver Biopsy:
- granular eosinophilic “ground glass” appearance
- cytotoxic T cells mediate damage
- defective virus—depends on HBV HBsAg coat for entry into hepatocytes
HDV
Deltavirus, Defective
Hepatitis Viruses:
- RNA Hepevirus
- fecal-oral route, especially waterborne
- Incubation Period—short
- fulminant hepatitis in expectant (pregnant) women
- high mortality in pregnant women
- no risk for HCC
- Liver Biopsy:
- patchy necrosis
- enteric
- epidemic
- no carrier state
HEV
Expectant, Enteric, Epidemic
Extrahepatic Hepatitis Viruses:
- Aplastic Anemia
- Membranous GN > Membranoproliferative GN
- Polyarteritis Nodosa
Hepatitis B
Extrahepatic Hepatitis Viruses:
- Essential Mixed Cryoglobulinemia
- ↑ risk B-cell NHL
- ITP
- Autoimmune Hemolytic Anemia
- Membranoproliferative GN > Membranous GN
- Leukocytoclastic Vasculitis
- Sporadic Porphyria Cutanea Tarda
- Lichen Planus
- ↑ risk of Diabetes Mellitus
- Autoimmune Hypothyroidism
Hepatitis C
Hepatitis Serologic Markers
Hepatitis Serologic Markers:
best test to detect acute hepatitis A
Anti-HAV (IgM)
Hepatitis Serologic Markers:
- indicates prior HAV infection and/or prior vaccination
- protects against reinfection
Anti-HAV (IgG)
Hepatitis Serologic Markers:
- antigen found on surface of HBV
- indicates hepatitis B infection
HBsAg
Hepatitis Serologic Markers:
indicates immunity to hepatitis B due to vaccination or recovery from infection
Anti-HBs
Hepatitis Serologic Markers:
antigen associated with core of HBV
HBcAg
Hepatitis Serologic Markers:
- IgM = acute/recent infection
- IgG = prior exposure or chronic infection
- IgM may be the sole ⊕ marker of infection during window period
Anti-HBc
Hepatitis Serologic Markers:
- secreted by infected hepatocyte into circulation
- not part of mature HBV virion
- indicates active viral replication and therefore high transmissibility and poorer prognosis
HBeAg
Hepatitis Serologic Markers:
indicates low transmissibility
Anti-HBe
HIV
HIV has _____ genome (2 molecules of RNA).
Diploid
HIV Structural Genes and Proteins
-
env (gp120 and gp41):
- formed from cleavage of gp160 to form envelope glycoproteins
- gp120—attachment to host CD4+ T cell
- gp41—fusion and entry
-
gag (p24 and p17)
- capsid and matrix proteins, respectively
-
pol
- reverse transcriptase, aspartate protease, integrase
HIV _____ synthesizes dsDNA from genomic RNA; dsDNA integrates into host genome.
Reverse Transcriptase
HIV binds _____ as well as a coreceptor, either _____ on macrophages (early infection) or _____ on T cells (late infection).
CD4
Coreceptors
- CCR5 on macrophages (early infection)
- CXCR4 on T cells (late infection)
HIV:
homozygous CCR5 mutation
Immunity
HIV:
heterozygous CCR5 mutation
slower course
HIV Diagnosis:
- presumptive diagnosis
- detect viral p24 Ag capsid protein and IgG Abs to HIV-1/2
- very high sensitivity/specificity
HIV-1/2 Ag/Ab Immunoassays
HIV Diagnosis:
- confirmation of ⊕ HIV-1/2 Ag/Ab immunoassay tests
- determine whether patient has HIV-1 or HIV-2
HIV-1/2 Ab-Differentiation Immunoassays
HIV Diagnosis:
- done if inconclusive differentiation assay
- if ⊝, patient had false positive initial Ag/Ab immunoassay
HIV‑1 Nucleic Acid Amplification Test (NAAT)
HIV Diagnosis:
- determine the amount of viral RNA in the plasma
- high levels are associated with poor prognosis
- used to monitor effect of drug therapy
Viral Load Tests
HIV Diagnosis:
determine appropriate therapy
HIV Genotyping
HIV Diagnosis:
AIDS CD4 levels
≤ 200 CD4+ cells/mm3
*HIV ⊕ with AIDS-defining condition (eg. Pneumocystis pneumonia) or CD4+ percentage < 14%
(normal: 500–1500 cells/mm3)
HIV-1/2 Ag/Ab testing is not recommended in babies with suspected HIV due to maternally transferred antibodies. _____ is used instead.
HIV Viral Load
Time Course of Untreated HIV Infection
- Dashed lines on CD4+ count axis indicate moderate immunocompromise (< 400 CD4+ cells/mm3) and when AIDS-defining illnesses emerge (< 200 CD4+ cells/mm3).
- Most patients who do not receive treatment eventually die of complications of HIV infection.
- During clinical latency phase, the virus replicates in lymph nodes.
Four Stages of Untreated HIV:
- Flu-like (acute)
- Feeling fine (latent)
- Falling count
- Final crisis
Common Diseases of HIV⊕ Adults:
CD4+ cell count < 500/mm3
- Candida albicans
- EBV
- HHV-8
- HPV
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 500/mm3
- Candida albicans
- scrapable white plaque
- pseudohyphae on microscopy
Oral Thrush
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 500/mm3
- EBV
- unscrapable white plaque on lateral tongue
Oral Hairy Leukoplakia
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 500/mm3
- HHV-8
- biopsy with lymphocytic inflammation
Kaposi Sarcoma
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 500/mm3
- HPV
Squamous Cell Carcinoma
- commonly of anus—men who have sex with men
- cervix—women
Common Diseases of HIV⊕ Adults:
CD4+ cell count < 200/mm3
- Histoplasma capsulatum
- HIV
- JC Virus (reactivation)
- Pneumocystis jirovecii
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 200/mm3
- fever, weight loss, fatigue, cough, dyspnea, nausea, vomiting, diarrhea
- oval yeast cells within macrophages
Histoplasma capsulatum
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 200/mm3
- HIV
Dementia
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 200/mm3
- JC Virus (reactivation)
- nonenhancing areas of demyelination on MRI
Progressive Multifocal Leukoencephalopathy
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 200/mm3
- pneumonia
- “ground-glass” opacities on CXR
Pneumocystis jirovecii
Common Diseases of HIV⊕ Adults:
CD4+ cell count < 100/mm3
- Aspergillus fumigatus
- Bartonella henselae
- Candida albicans
- CMV
- Cryptococcus neoformans
- Cryptosporidium spp.
- EBV
- Mycobacterium avium–intracellulare (Mycobacterium avium Complex)
- Toxoplasma gondii
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 100/mm3
- hemoptysis, pleuritic pain
- cavitation or infiltrates on chest imaging
Aspergillus fumigatus
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 100/mm3
- Bartonella henselae
- biopsy with neutrophilic inflammation
Bacillary Angiomatosis
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 100/mm3
- Candida albicans
- white plaques on endoscopy
- yeast and pseudohyphae on biopsy
Esophagitis
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 100/mm3
- retinitis, esophagitis, colitis, pneumonitis, encephalitis
- linear ulcers on endoscopy, cotton-wool spots on fundoscopy
- biopsy reveals cells with intranuclear (owl eye) inclusion bodies
CMV
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 100/mm3
- meningitis
- encapsulated yeast on India ink stain or capsular antigen ⊕
Cryptococcus neoformans
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 100/mm3
- chronic, watery diarrhea
- acid-fast oocysts in stool
Cryptosporidium spp.
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 100/mm3
- B-cell lymphoma (eg. non-Hodgkin lymphoma, CNS lymphoma)
- CNS lymphoma—ring enhancing, may be solitary (vs. Toxoplasma)
EBV
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 100/mm3
- nonspecific systemic symptoms (fever, night sweats, weight loss) or focal lymphadenitis
Mycobacterium avium–intracellulare
(Mycobacterium avium Complex)
Common Diseases of HIV⊕ Adults:
- CD4+ cell count < 100/mm3
- brain abscesses
- multiple ring-enhancing lesions on MRI
Toxoplasma gondii
Prion diseases are caused by the conversion of a normal (predominantly α-helical) protein termed prion protein (PrPc) to a _____, which is transmissible via CNS-related tissue (iatrogenic CJD) or food contaminated by BSE-infected animal products (variant CJD).
β-pleated form (PrPsc)
Prion Diseases:
transmissible via CNS-related tissue
Iatrogenic CJD
Prion Diseases:
transmissible via food contaminated by BSE-infected animal products
Variant CJD
PrPsc resists _____ and facilitates the conversion of still more PrPc to PrPsc.
protease degradation
Prions are resistant to standard sterilizing procedures, including standard _____.
autoclaving
Accumulation of PrPsc results in _____.
- spongiform encephalopathy
- dementia
- ataxia
- death
Prion Diseases:
- rapidly progressive dementia
- typically sporadic (some familial forms)
Creutzfeldt-Jakob Disease
Prion Diseases:
also known as “mad cow disease”
Bovine Spongiform Encephalopathy
Prion Diseases:
acquired prion disease noted in tribal populations practicing human cannibalism
Kuru
Normal Flora:
skin
S. epidermidis
Normal Flora:
nose
- S. epidermidis
- S. aureus
Normal Flora:
oropharynx
Viridans Group Streptococci
Normal Flora:
dental plaque
S. mutans
Normal Flora:
colon
- B. fragilis
- E. coli
Normal Flora:
vagina
- Lactobacillus
- E. coli
- Group B Strep
_____ food poisoning starts quickly and ends quickly.
- S. aureus
- B. cereus
Bugs Causing Foodborne Illness:
reheated rice
B. cereus
“Food poisoning from reheated rice? Be serious!”
Bugs Causing Foodborne Illness:
- improperly canned foods (toxins)
- raw honey (spores)
C. botulinum
Bugs Causing Foodborne Illness:
reheated meat
C. perfringens
Bugs Causing Foodborne Illness:
undercooked meat
E. coli O157:H7
Bugs Causing Foodborne Illness:
- deli meats
- soft cheeses
L. monocytogenes
Bugs Causing Foodborne Illness:
- poultry
- meat
- eggs
Salmonella
Bugs Causing Foodborne Illness:
- meats
- mayonnaise
- custard
- preformed toxin
S. aureus
Bugs Causing Foodborne Illness:
contaminated seafood
- V. parahaemolyticus
- V. vulnificusa
_____ can cause wound infections from contact with contaminated water or shellfish.
V. vulnificus
Bugs Causing Bloody Diarrhea:
- comma- or S-shaped organisms
- growth at 42°C
Campylobacter
Bugs Causing Bloody Diarrhea:
- protozoan
- amebic dysentery
- liver abscess
E. histolytica
Bugs Causing Bloody Diarrhea:
- O157:H7
- can cause HUS
- makes Shiga-like toxin
Enterohemorrhagic E. coli
Bugs Causing Bloody Diarrhea:
invades colonic mucosa
Enteroinvasive E. coli
Bugs Causing Bloody Diarrhea:
- lactose ⊝
- flagellar motility
- has animal reservoir
- especially poultry and eggs
Salmonella (nontyphoidal)
Bugs Causing Bloody Diarrhea:
- lactose ⊝
- very low ID50
- produces Shiga toxin (human reservoir only)
- bacillary dysentery
Shigella
Bugs Causing Bloody Diarrhea:
- day care outbreaks
- pseudoappendicitis
Y. enterocolitica
Bugs Causing Watery Diarrhea:
- pseudomembranous colitis
- associated with antibiotics and PPIs
- occasionally bloody diarrhea
C. difficile
Bugs Causing Watery Diarrhea:
also causes gas gangrene
C. perfringens
Bugs Causing Watery Diarrhea:
- travelers’ diarrhea
- heat-labile (LT) toxin
- heat-stable (ST) toxin
Enterotoxigenic E. coli
Bugs Causing Watery Diarrhea:
protozoa
- Giardia
- Cryptosporidium
Bugs Causing Watery Diarrhea:
- comma-shaped organisms
- rice-water diarrhea
- often from infected seafood
V. cholerae
Bugs Causing Watery Diarrhea:
viruses
- Rotavirus
- Norovirus
- Enteric Adenovirus
Common Causes of Pneumonia:
Neonates (< 4 wks.)
- Group B Streptococci
- E. coli
Common Causes of Pneumonia:
Children (4 wks.-18 yrs.)
Runts May Cough Chunky Sputum
- Viruses (RSV)
- Mycoplasma
- C. trachomatis (infants–3 yr.)
- C. pneumoniae (school-aged children)
- S. pneumoniae
Common Causes of Pneumonia:
Adults (18-40 yrs.)
- Mycoplasma
- C. pneumoniae
- S. pneumoniae
- Viruses (eg. influenza)
Common Causes of Pneumonia:
Adults (40-65 yrs.)
- S. pneumoniae
- H. influenzae
- Anaerobes
- Viruses
- Mycoplasma
Common Causes of Pneumonia:
Elderly
- S. pneumoniae
- Influenza Virus
- Anaerobes
- H. influenzae
- Gram ⊝ Rods
Common Causes of Pneumonia:
Alcoholics
- Klebsiella
- Anaerobes—usually due to aspiration (eg. Peptostreptococcus, Fusobacterium, Prevotella, Bacteroides)
Common Causes of Pneumonia:
IV Drug Users
- S. pneumoniae
- S. aureus
Common Causes of Pneumonia:
Aspiration
Anaerobes
Common Causes of Pneumonia:
Atypical
- Mycoplasma
- Chlamydophila
- Legionella
- Viruses (RSV, CMV, Influenza, Adenovirus)
Common Causes of Pneumonia:
Cystic Fibrosis
- Pseudomonas
- S. aureus
- S. pneumoniae
- Burkholderia cepacia
Common Causes of Pneumonia:
Immunocompromised
- S. aureus
- Enteric Gram ⊝ Rods
- Fungi
- Viruses
- P. jirovecii (with HIV)
Common Causes of Pneumonia:
Nosocomial (hospital acquired)
- S. aureus
- Pseudomonas
- Enteric Gram ⊝ Rods
Common Causes of Pneumonia:
Postviral
- S. pneumoniae
- S. aureus
- H. influenzae
Common Causes of Meningitis:
Newborns (0-6 mos.)
- Group B Streptococci
- E. coli
- Listeria
Common Causes of Meningitis:
Children (6 mos.-6 yrs.)
- S. pneumoniae
- N. meningitidis
- H. influenzae type b
- Enteroviruses
Common Causes of Meningitis:
6-60 yrs.
- S. pneumoniae
- N. meningitidis (#1 in teens)
- Enteroviruses
- HSV
Common Causes of Meningitis:
60+ yrs.
- S. pneumoniae
- Gram ⊝ Rods
- Listeria
Meningitis is empirically treated with _____.
- Ceftriaxone
- Vancomycin
- Ampicillin—if Listeria is suspected
Viral Causes of Meningitis
- Enteroviruses (especially coxsackievirus)
- HSV-2 (HSV-1 = encephalitis)
- HIV
- West Nile Virus (also causes encephalitis)
- VZV
Common Causes of Meningitis:
HIV
Cryptococcus spp.
Cerebrospinal Fluid Findings in Meningitis:
- ↑ opening pressure
- ↑ PMNs
- ↑ protein
- ↓ glucose
Bacterial
Cerebrospinal Fluid Findings in Meningitis:
- ↑ opening pressure
- ↑ lymphocytes
- ↑ protein
- ↓ glucose
- Fungal
- TB
Cerebrospinal Fluid Findings in Meningitis:
- normal/↑ opening pressure
- ↑ lymphocytes
- normal/↑ protein
- normal glucose
Viral
Infections Causing Brain Abscess:
most common
- Viridans Streptococci
- Staphylococcus aureus
Infections Causing Brain Abscess:
dental infection or extraction
Oral Anaerobes
Infections Causing Brain Abscess:
multiple abscesses
Bacteremia
Infections Causing Brain Abscess:
single lesions
Contiguous Sites:
- otitis media and mastoiditis → temporal lobe and cerebellum
- sinusitis or dental infection → frontal lobe
Infections Causing Brain Abscess:
AIDS
Toxoplasma Reactivation
Osteomyelitis:
most common
S. aureus
Osteomyelitis:
sexually active
Neisseria gonorrhoeae
- rare
- septic arthritis more common
Osteomyelitis:
Sickle Cell Disease
- Salmonella
- S. aureus
Osteomyelitis:
prosthetic joint replacement
- S. aureus
- S. epidermidis
Osteomyelitis:
vertebral involvement
- S. aureus
- Mycobacterium tuberculosis (Pott disease)
Osteomyelitis:
cat and dog bites
Pasteurella multocida
Osteomyelitis:
IV drug abuse
- S. aureus
- Pseudomonas
- Candida
_____ are insensitive early but can be useful in chronic osteomyelitis.
Radiographs
_____ is best for detecting acute osteomyelitis and detailing anatomic involvement.
MRI
Cystitis presents with _____.
- dysuria
- frequency
- urgency
- suprapubic pain
- WBCs (but not WBC casts) in urine
Cystitis is primarily caused by _____.
ascension of microbes from urethra to bladder
Ascension of microbes from the urethra to the kidneys results in pyelonephritis, which presents with _____.
- fever
- chills
- flank pain
- costovertebral angle tenderness
- hematuria
- WBC casts
Urinary tract infections are ten times more common in women due to _____.
shorter urethras colonized by fecal flora
Predisposing Factors to UTI
- female
- males with congenital defects or vesicoureteral reflux
- obstruction
- kidney surgery
- catheterization
- GU malformation
- diabetes
- pregnancy
- elderly—enlarged prostate
Urinary Tract Infections:
- leading cause of UTI
- colonies show strong pink lactose-fermentation on MacConkey agar
Escherichia coli
Urinary Tract Infections:
2nd leading cause of UTI in sexually active women
Staphylococcus saprophyticus
Urinary Tract Infections:
- 3rd leading cause of UTI
- large mucoid capsule
- viscous colonies
Klebsiella pneumoniae
Urinary Tract Infections:
- some strains produce a red pigment
- often nosocomial and drug resistant
Serratia marcescens
Urinary Tract Infections:
often nosocomial and drug resistant
Enterococcus
Urinary Tract Infections:
- motility causes “swarming” on agar
- associated with struvite stones
Proteus mirabilis
Urinary Tract Infections:
- blue-green pigment
- fruity odor
- usually nosocomial and drug resistant
Pseudomonas aeruginosa
UTI Diagnostic Markers:
evidence of WBC activity
Leukocyte Esterase
UTI Diagnostic Markers:
reduction of urinary nitrates by bacterial species (eg. E coli)
Nitrite Test
UTI Diagnostic Markers:
urease-producing bugs (eg. S. saprophyticus, Proteus, Klebsiella)
Urease Test
Common Vaginal Infections:
- no inflammation
- thin, white discharge with fishy odor
- clue cells
- pH > 4.5
Bacterial Vaginosis
Bacterial Vaginosis is treated with _____.
- Metronidazole
- Clindamycin
Common Vaginal Infections:
- inflammation (“strawberry cervix”)
- frothy, yellow-green, foul-smelling discharge
- motile trichomonads
- pH > 4.5
Trichomonas Vaginitis
Trichomonas Vaginitis is treated with _____.
- Metronidazole
- treat sexual partner(s)
Common Vaginal Infections:
- inflammation
- thick, white, “cottage cheese” discharge
- pseudohyphae
- pH normal (4.0–4.5)
Candida Vulvovaginitis
Candida Vulvovaginitis is treated with _____.
Azoles
ToRCHeS Infections
- Toxoplasma gondii
- Rubella
- Cytomegalovirus
- HIV
- Herpes Simplex Virus-2
- Syphilis
Transmission of ToRCHeS infections is _____ in most cases, or via _____ (especially HSV-2).
- transplacental
- delivery
*Other important infectious agents include Streptococcus agalactiae (group B streptococci), E. coli, and Listeria monocytogenes—all causes of meningitis in neonates.
*Parvovirus B19 causes hydrops fetalis.
Nonspecific Signs of ToRCHeS Infections
- hepatosplenomegaly
- jaundice
- thrombocytopenia
- growth retardation
ToRCHeS Infections:
-
Mode of Transmission:
- cat feces
- ingestion of undercooked meat
-
Maternal Symptoms:
- usually asymptomatic
- lymphadenopathy (rarely)
-
Neonatal Symptoms:
- Classic Triad:
- chorioretinitis
- hydrocephalus
- intracranial calcifications
- +/− “blueberry muffin” rash
- Classic Triad:
Toxoplasma gondii
ToRCHeS Infections:
-
Mode of Transmission:
- respiratory droplets
-
Maternal Symptoms:
- rash
- lymphadenopathy
- polyarthritis
- polyarthralgia
-
Neonatal Symptoms:
- Classic Triad:
- cataracts
- deafness
- congenital heart disease (PDA)
- ± “blueberry muffin” rash
- Classic Triad:
Rubella
“I (eye) ♥ ruby (rubella) earrings.”
ToRCHeS Infections:
-
Mode of Transmission:
- sexual contact
- organ transplants
-
Maternal Symptoms:
- usually asymptomatic
- mononucleosis-like illness
-
Neonatal Symptoms:
- hearing loss
- seizures
- petechial rash
- “blueberry muffin” rash
- chorioretinitis
- periventricular calcifications
Cytomegalovirus
ToRCHeS Infections:
-
Mode of Transmission:
- sexual contact
- needlestick
-
Maternal Symptoms:
- variable presentation depending on CD4+ cell count
-
Neonatal Symptoms:
- recurrent infections
- chronic diarrhea
HIV
ToRCHeS Infections:
-
Mode of Transmission:
- skin or mucous membrane contact
-
Maternal Symptoms:
- usually asymptomatic
- herpetic (vesicular) lesions
-
Neonatal Symptoms:
- meningoencephalitis
- herpetic (vesicular) lesions
Herpes Simplex Virus-2
ToRCHeS Infections:
-
Mode of Transmission:
- sexual contact
-
Maternal Symptoms:
- chancre (1°)
- disseminated rash (2°)
-
Neonatal Symptoms:
- stillbirth
- hydrops fetalis
- facial abnormalities (eg. notched teeth, saddle nose, short maxilla)
- saber shins
- CN VIII deafness
Syphilis
Red Rashes of Childhood:
- Hand-Foot-Mouth Disease
- oval-shaped vesicles on palms and soles
- vesicles and ulcers in oral mucosa
Coxsackievirus type A
Red Rashes of Childhood:
- Roseola (Exanthem Subitum)
- symptomatic rose-colored macules appear on body after several days of high fever
- can present with febrile seizures
- usually affects infants
Human Herpesvirus 6
Red Rashes of Childhood:
- Rubeola
- confluent rash beginning at head and moving down
- preceded by cough, coryza, conjunctivitis, and blue-white (Koplik) spots on buccal mucosa
Measles Virus
Red Rashes of Childhood:
- Erythema Infectiosum (Fifth Disease)
- “slapped cheek” rash on face B (can cause hydrops fetalis in pregnant women)
Parvovirus B19
Red Rashes of Childhood:
- pink macules and papules begin at head and move down, remain discrete → fine desquamating truncal rash
- postauricular lymphadenopathy
Rubella Virus
Red Rashes of Childhood:
- Scarlet Fever
- flushed cheeks and circumoral pallor on the face
- erythematous, sandpaper-like rash from neck to trunk and extremities
- fever and sore throat
Streptococcus pyogenes
Red Rashes of Childhood:
- Chickenpox
- vesicular rash begins on trunk
- spreads to face and extremities with lesions of different stages
Varicella-Zoster Virus
Sexually Transmitted Infections:
- opportunistic infections
- Kaposi sarcoma
- lymphoma
- HIV
AIDS
Sexually Transmitted Infections:
- painful genital ulcer with exudate
- inguinal adenopathy
- Haemophilus ducreyi
Chancroid
It’s so painful, you “do cry”.
Sexually Transmitted Infections:
- urethritis
- cervicitis
- epididymitis
- conjunctivitis
- reactive arthritis
- PID
Chlamydia trachomatis (D–K)
Sexually Transmitted Infections:
- Condylomata Acuminata
- genital warts
- koilocytes
HPV-6 and -11
Sexually Transmitted Infections:
- Genital Herpes
- painful penile, vulvar, or cervical vesicles and ulcers
- can cause systemic symptoms such as fever, headache, and myalgia
HSV-2, less commonly HSV-1
Sexually Transmitted Infections:
- urethritis
- cervicitis
- PID,
- prostatitis
- epididymitis
- arthritis
- creamy purulent discharge
Neisseria gonorrhoeae
Sexually Transmitted Infections:
- painless, beefy red ulcer that bleeds readily on contact
- uncommon in US
- Klebsiella (Calymmatobacterium) granulomatis
- cytoplasmic Donovan bodies (bipolar staining) seen on microscopy
Granuloma Inguinale
(Donovanosis)
Sexually Transmitted Infections:
- jaundice
- HBV
Hepatitis B
Sexually Transmitted Infections:
- infection of lymphatics
- painless genital ulcers
- painful lymphadenopathy (ie. buboes)
- Chlamydia trachomatis (L1–L3)
Lymphogranuloma Vvenereum
Sexually Transmitted Infections:
- painless chancre
- Treponema pallidum
Primary Syphilis
Sexually Transmitted Infections:
- fever
- lymphadenopathy
- skin rashes
- condylomata lata
- Treponema pallidum
Secondary Syphilis
Sexually Transmitted Infections:
- gummas
- tabes dorsalis
- general paresis
- aortitis
- Argyll Robertson pupil
- Treponema pallidum
Tertiary Syphilis
Sexually Transmitted Infections:
- vaginitis
- strawberry cervix
- motile in wet prep
Trichomonas vaginalis
_____ presents with cervical motion tenderness, adnexal tenderness, purulent cervical discharge.
Pelvic Inflammatory Disease
Pelvic Inflammatory Disease may include _____.
- salpingitis
- endometritis
- hydrosalpinx
- tubo-ovarian abscess
Pelvic Inflammatory Disease:
Pathogens
-
Chlamydia trachomatis
- subacute
- often undiagnosed
- most common bacterial STI in the US
-
Neisseria gonorrhoeae
- acute
_____ is a risk factor for ectopic pregnancy, infertility, chronic pelvic pain, and adhesions.
Salpingitis
Pelvic inflammatory disease can lead to _____ (perihepatitis)—infection and inflammation of the liver capsule and “violin string” adhesions of peritoneum to liver.
Fitz-Hugh-Curtis Syndrome
_____ are the most common causes nosocomial infections.
- E. coli (UTI)
- S. aureus (wound infection)
Nosocomial Infections:
- antibiotic use
- watery diarrhea
- leukocytosis
Clostridium difficile
Nosocomial Infections:
- aspiration (2° to altered mental status, old age)
- right lower lobe infiltrate or right upper/middle lobe (patient recumbent)
- purulent malodorous sputum
- Polymicrobial
- Gram ⊝ Bacteria
- Anaerobes
Nosocomial Infections:
- decubitus ulcers
- surgical wounds
- drains
- erythema, tenderness, induration, and drainage from surgical wound sites
- S. aureus (including MRSA)
- Gram ⊝ Anaerobes
- Bacteroides
- Prevotella
- Fusobacterium
Nosocomial Infections:
- intravascular catheters
- erythema, induration, tenderness, and drainage from access sites
- S. aureus (including MRSA)
- S. epidermidis (long term)
- Enterobacter
Nosocomial Infections:
- mechanical ventilation
- endotracheal intubation
- new infiltrate on CXR
- ↑ sputum production
- sweet odor
- P. aeruginosa (sweet odor)
- Klebsiella
- Acinetobacter
- S. aureus
Nosocomial Infections:
- renal dialysis unit
- needlestick
- HBV
- HCV
Nosocomial Infections:
- urinary catheterization
- dysuria
- leukocytosis
- flank pain
- costovertebral angle tenderness
Infections in your PEcKer
- Proteus spp.
- E. coli
- Klebsiella
Nosocomial Infections:
- water aerosols
- signs of pneumonia
- GI symptoms (diarrhea, nausea, vomiting)
- neurologic abnormalities
Legionella
Bugs Affecting Unvaccinated Children:
- rash beginning at head and moving down
- postauricular lymphadenopathy
Rubella Virus
Bugs Affecting Unvaccinated Children:
- rash beginning at head and moving down
- rash preceded by cough, coryza, conjunctivitis, and blue-white (Koplik) spots on buccal mucosa
Measles Virus
Bugs Affecting Unvaccinated Children:
- meningitis
- microbe colonizes nasopharynx
H. influenzae type b
Bugs Affecting Unvaccinated Children:
- meningitis
- can also lead to myalgia and paralysis
Poliovirus
Bugs Affecting Unvaccinated Children:
- epiglottitis
- fever with dysphagia, drooling, and difficulty breathing due to edematous “cherry red” epiglottis
- “thumbprint sign” on x-ray
- also capable of causing epiglottitis in fully immunized children
H. influenzae type b
Bugs Affecting Unvaccinated Children:
- pharyngitis
- grayish oropharyngeal exudate
- “pseudomembranes” may obstruct airway
- painful throat
- elaborates toxin that causes necrosis in pharynx, cardiac, and CNS tissue
Corynebacterium diphtheriae
Pathogens:
asplenic patient (due to surgical splenectomy or autosplenectomy, eg. chronic sickle cell disease)
Encapsulated Microbes
- *SHiN**
- S. pneumoniae* >> H. influenzae type b > N. meningitidis
Pathogens:
- branching rods in oral infection
- sulfur granules
Actinomyces israelii
Pathogens:
chronic granulomatous disease
Catalase ⊕ Microbes
- especially S. aureus
Pathogens:
“currant jelly” sputum
Klebsiella
Pathogens:
dog or cat bite
Pasteurella multocida
Pathogens:
- facial nerve palsy (typically bilateral)
- Lyme disease
Borrelia burgdorferi
Pathogens:
fungal infection in diabetic or immunocompromised patient
Mucor or Rhizopus spp.
Pathogens:
health care provider
- HBV
- HCV (from needlestick)
Pathogens:
neutropenic patients
- Candida albicans (systemic)
- Aspergillus
Pathogens:
organ transplant recipient
CMV
Pathogens:
- Periodic Acid–Schiff (PAS) ⊕
- Whipple disease
Tropheryma whipplei
Pathogens:
- pediatric infection
- epiglottitis
Haemophilus influenzae
Pathogens:
- pneumonia in cystic fibrosis
- burn infection
Pseudomonas aeruginosa
Pathogens:
- pus
- empyema
- abscess
S. aureus
Pathogens:
rash on hands and feet
- Coxsackie A Virus
- Treponema pallidum
- Rickettsia rickettsii
Pathogens:
sepsis/meningitis in newborn
Group B Strep
Pathogens:
surgical wound
S. aureus
Pathogens:
traumatic open wound
Clostridium perfringens
