Microbiology Flashcards
Stain and shape of Chlamydiae
G(-) pleomorphic
Giemsa stain
Stain and shape of Mycobacterium
G(+) rod
Acid fast
Stain and shape of Proteus
G(-) rod
Stain and shape of Klebsiella
G(-) rod
Stain and shape of Vibrio
G(-) rod
Stain and shape of Haemophilus
G(-) rod (pleomorphic)
Respiratory
Stain and shape of Shigella
G(-) rod
Stain and shape of Bartonella
G(-) rod
Zoonotic
Stain and shape of Clostridium
G(+) rod
Stain and shape of Staphylococcus
G(+) coccus
Clusters
Stain and shape of Propionibacterium
G(+) rod
Stain and shape of E. coli
G(-) rod
Stain and shape of Corynebacterium
G(+) rod
Stain and shape of Bacillus
G(+) rod
What are hyphae?
Hyphae are the long, filamentous outgrowths from fungus that are the primary way that they invade. This makes the fungus a multicellular organism in that each hyphae is a new cell.
Remember that yeasts are unicellular and do not grow as hyphae. They may not bud off perfectly and therefore would form pseudohyphae.
Stain and shape of Treponema
G(-) Spirochete
Stain and shape of Campylobacter
G(-) rod
Stain and shape of Neisseria
G(-) coccus
Stain and shape of Borrelia
G(-) Spirochete
Giemsa stain
Stain and shape of Burkholderia cepacia
G(-) rod
Respiratory
Stain and shape of Moraxella catarrhalis
G(-) coccus
Stain and shape of Rickettsiae
G(-) pleomorphic
Giemsa stain
Stain and shape of Enterobacter
G(-) rod
Stain and shape of Pseudomonas
G(-) rod
Stain and shape of Listeria
G(+) rod
Stain and shape of Ureaplasma
No cell wall, doesn’t gram stain
Stain and shape of Legionella
G(-) rod
Respiratory
Stain and shape of Bordetella
G(-) rod
Respiratory
Stain and shape of Brucella
G(-) rod
Zoonotic
Stain and shape of Helicobacter
G(-) rod
Stain and shape of Actinomyces
G(+)
Branching filamentous
Stain and shape of Leptospira
G(-) Spirochete
Stain and shape of Nocardia
G(+) (weakly acid fast)
Branching filamentous
Stain and shape of Gardnerella
G(+) rod
Gram variable
Stain and shape of Pasteurella
G(-) rod
Zoonotic
Stain and shape of Bacteroides
G(-) rod
Stain and shape of Lactobacillus
G(+) rod
Stain and shape of Salmonalla
G(-) rod
Stain and shape of Yersinia
G(-) rod
Stain and shape of Francisella
G(-) rod
Zoonotic
Stain and shape of Streptococcus
G(+) coccus
chains or pairs
Stain and shape of Mycoplasma
No cell wall, doesn’t gram stain
Stain and shape of Serratia
G(-) rod
Name classic G(-) cocci
Moraxella catarrhalis
Neisseria
Name G(+) rods
Bacillus Clostridium Corynebacterium Gardnerella (Gram Variable) Lactobacillus Listeria Mycobacterium (acid fast) Propionibacterium
Name gram negative enteric bacteria
B. C. PPEESSSKY H. V. Bacteroides Camylobacter Proteus Pseudomonas E. coli Enterobacter Salmonella Shigella Serratia Klebsiella Yersinia Helicobacter Vibrio
Name the G(-) Respiratory bacteria
Bordetella
Burkholderia cepacia
Haemophilus (Pleomorphic)
Legionella (silver stain)
Name the G(-) Zoonotic bacteria
Bartonella
Brucella
Francisella
Pasteurella
Name the branching filamentous G(+) bacteria
Actinomyces
Nocardia (weakly acid fast)
Name the pleomorphic G(-) bacteria
Chlamydia (Giemsa)
Rickettsiae (Giemsa)
Name the G(-) spirochetes
Borrelia (Giemsa)
Leptospira
Treponema
What bacteria have no cell wall and therefore gram stain not at all?
Mycoplasma
Ureaplasma
What bac do not gram stain well?
(These Microbes May Lack Real Color) Treponema, Leptospira Mycobacteria Mycoplasma, Ureaplasma Legionella Rickettsia Chlamydia Bartonella Ehrlichia Anaplasma
What bugs stain with Giemsa stain?
(Certain Bugs Really Try my Patience) Chlamydia Borrelia Rickettsia Trypanosomes Plasmodium
What does Periodic Acid Schiff stain?
Glycogen, mucopolysaccharides;
Used to diagnose Whipple disease
Think PaSs the SUGAR
Ziehl-Neelsen Stain
Acid fast bacteria: Mycobacteria, Nocardia
Protozoa like Cryptosporidium oocysts
India ink stain
Stains Cryptococcus neoformans
Also stains polysaccharide capsules red
Silver stain
Used for fungi like Coccidioides and Pneumocystis
Also Legionella, Helicobacter pylori
Media used for H. flu isolation
Chocolate agar
Media used for Neisseria isolation
Thayer-Martin agar
Selectively favors growth of Neisseria by containing vancomycin, Trimethoprim, Colistin, Nystatin
Use of MacConkey agar
Contains an indicator that turns pink with certain pH
Identifies lactose fermenting enteric bacteria
Agar for E. coli
Eosin–methylene blue agar
Colonies with green metallic sheen
Agar used for fungus
Sabouraud agar
Sab’s a fun guy
What group of bacteria are not susceptible to aminoglycosides?
Anaerobic because these drugs require O2 to enter the bac cell
Think: aminO2glycosides
Aerobic or Anaerobic?
Nocardia
Aerobic
Aerobic or Anaerobic?
Fusobacterium
Anaerobic
Aerobic or Anaerobic?
Mycobacterium tuberculosis
Aerobic
Apices of lungs
Aerobic or Anaerobic?
Pseudomonas
Aerobic
Aerobic or Anaerobic?
Actinomyces
Anaerobic
Aerobic or Anaerobic?
Bacteroides
Anaerobic
Aerobic or Anaerobic?
Clostridium
Anaerobic
General features of anaerobic bacteria besides not liking O2
Lack catalase and/or superoxide dismutase–why they can’t handle O2
Generally foul smelling
Difficult to culture
Produce gas in tissues (CO2, H2)
They are normal flora in the gut, but pathologic elsewhere
Not susceptible to aminoglycosides
What is catalase?
Converts H2O2 to H2O and O2
Found in most organisms exposed to O2
Predominant agents in neonatal bacterial meningitis
Streptococcus agalactiae
E. coli
Listeria monocytogens
Most common bacterial meningitis agents in descending order and age groups
Strep. pneumo: every age
Strep. agalactiae (group B strep): neonates
Neisseria meningitidis: kids to middle-age adults
Listeria monocytogens: Infants, elderly
H. influenzae: 1 mo to 18 yr
Catalase and coagulase in regard to Staph.
All staph species are catalase positive Coagulase Negative Staph (CoNS) are common skin flora and used to be thought as non-pathogenic. Now, they are known as common cause of bacteremia, and nosocomial infections of prosthetic devices such as heart valves and hip replacements by forming a slime/biofilm S. aureus is coagulase positive S. epidermidis is coagulase negative S. saprophyticus also CoNS
What bacterial species is associated with rusty sputum?
Pneumococcus (Strep. pneumoniae)
Common cause of meningitis, otitis media, pneumonia, sinusitis
What is the primary test for differentiating between Staph and Strep?
Catalase test
Staph–positive
Strep–negative
What is the primary bacteria considered when faced with and infection associated with an indwelling catheter, prosthetic heart valve, or other implanted device like a hip replacement?
Coagulase negative staph
Staph. epidermidis
Treatment choice for natural valve endocarditis vs prosthetic valve
Prosthetic valve often by coagulase neg staph of which most are resistant to methicillin and penicillin and are best treated with vancomycin first, and possibly Gentamicin or Rifampin later
Native valve treated with Nafcillin or Oxacillin
What bug can cause congenital cataracts?
Rubella infection in utero
What are the common effects in a neonate of in utero infection with CMV?
Chorioretinitis Sensorineural deafness Seizures Jaundice HSM Microcephaly
What is inclusion conjunctivitis and what causes it?
Conjunctivitis presenting often with a follicular response mostly on the tarsal conjunctiva caused by Chlamydia trachomatis
Most often caused by new sex partner within last 2 months, also from poorly treated swimming pools
Also affects newborns
Listeria monocytogenes
G(+) rod, facultative intracellular
Acquired most commonly from unpasteurized dairy or cold deli meats, transplacental, or vaginal during birth
Tumbling motility in broth
Can kill fetus, cause amnionitis, septicemia, neonatal and immune compromised meningitis
Treated with ampicillin
What bugs are associated with unpasteurized dairy?
Listeria
Brucella (undulating fever)
What bug characteristically has tumbling motility in broth?
Listeria monocytogenes
Patient with Sx of meningitis has purulent CSF and found to have intracellular G(+) bacilli. Likely Dx?
Listeria monocytogenes
Toxoplasma and meningitis
Usually immune compromised patients
Comes from cat feces most often, but can also come from undercooked lamb or pork
Estimated that 50% of world pop is infected with no Sx or problems
VDRL and RPR tests
Both are tests for syphilis
Venereal Disease Research Lab test
Rapid Plasma Reagin test
Considered nontreponemal tests because they look for Ab’s against nontreponemal antigens that indirectly indicate infection
Mix serum with cardiolipin, lecithin, cholesterol and look for flucculation
This is a sensitive screening test that is followed up with a confirmatory test called FTA-ABS for diagnosis
Significance of cold agglutinins
Indication of Mycoplasma infection
Blood placed in tube with anticoagulant then placed in cup of ice and seen to agglutinate at the lower temp and return to suspension when re-warmed
How to diagnose and test for syphilis
VDRL or RPR screening test then a definitive diagnostic test called FTA-ABS
Treatment strategy for N. gonorrhea and Chlamydia trachomatis
N. gonorrhea is showing lots of drug resistance and is therefore recommended to treat with a combination therapy including 3rd gen cephalosporin–Ceftriaxone with Azithromycin
Azithromycin is also beneficial because it covers Chlamydia which is frequently a co-infection with gonorrhea
What disease classically has intracellular gram(-) diplococci?
Neisseria gonorrhea
PID causes, treatments, complications
PID most commonly caused by N. gonorrhea and C. trachomatis
Treated with Ceftriaxone and Azithromycin
Inflammation can involve the endometrium and fallopian tubes and healing can lead to scarring of these locations which can lead to infertility (tubal-factor) and ectopic pregnancy
Enterococcus strains, identification, and features
Enterococcus is a reclassified strain of Strep making it G(+) cocci that grow in chains
Normal gut flora, includes E. faecalis and faecium
Commonly cause UTI, bacteremia, endocarditis, wound infection and others in a nosocomial setting
Very resistant to many drugs making them difficult to treat
Identified by G(+) cocci, catalase (-), gamma hemolytic, grows in bile and NaCl, PYR positive
What bacteria are G(+) cocci, catalase (-), and alpha hemolytic? How can they be differentiated?
Catalase (-) = Strep
Alpha hemolytic = Strep viridan or pneumoniae
Viridans: optochin resistant, bile insoluble, associated with dental caries and endocarditis after dental work
Pneumoniae: optochin sensitive, bile soluble, associated with pneumonia, meningitis, sinusitis, otitis media
What bacteria are G(+) cocci, catalase (-), and beta hemolytic, and how are they differentiated?
Catalase (-) = Strep
Beta hemolytic = pyogenes (GAS), agalactiae (GBS)
Pyogenes: PYR positive, bacitracin sensitive, associated with cellulitis, pharyngitis, erysipelas
Agalactiae: PYR negative, CAMP positive, associated with neonatal sepsis, pneumonia, meningitis, UTI
What bacteria produce pigments and what colors?
Staph aureus–yellow
Pseudomonas aeruginosa–blue-green
Serratia marcescens–red
Tzanck Smear
Test where lesions are scraped and examined under microscope looking for Tzanck cells or multinucleated giant cells
Used for: herpes, varicella and herpes zoster, pemphigus vulgaris, CMV
What are the toxins and effects of Bacillus anthracis?
Anthrax exotoxin
Edema factor: acts as adenylate cyclase increasing cAMP causing edema and phagocyte dysfunction
Lethal factor: zinc-dependent protease that causes apoptosis and physiological disruption
Toxins and effects of Bordetella pertussis
Pertusis toxin: disinhibits adenylate cyclase through Gi ADP-ribosylation increasing cAMP and causing edema and phagocyte dysfunction
Adenylate cyclase toxin: acts like adenylate cyclase increasing cAMP
Clostridium difficile toxins and effects
Toxin A: recruits and activates neutrophils that release cytokines causing inflammation, fluid loss and diarrhea
Toxin B: induces actin depolymerization causing mucosal cell death, bowel wall necrosis and pseudomembrane formation
Shigella dysenteriae toxin formation and effects
Shiga toxin: disable 60s ribosomal subunit stopping protein synthesis causing epithelial cell death and diarrhea
Strep. pyogenes toxins and effects
Pyrogenic exotoxin: superantigen, fever, shock, assoc. c scarlet fever and TSS
Streptolysin O and S: damages erythrocyte membranes causing beta hemolysis
Where is EHEC O157:H7 usually picked up? How is it different from other E coli?
Undercooked hamburger
Does not ferment sorbitol
Does not produce glucuronidase
What is hemolytic uremic syndrome?
Thrombocytopenia, microangiopathic hemolytic anemia, renal insufficiency
Can be caused by EHEC
How are EHEC and ETEC different?
ETEC produces heat-labile toxin (LT) and heat stable toxin (ST)
EHEC produce shiga-like toxin
Diptheria toxin
Catalyzes ADP-ribosylation of elongation factor 2 inactivating it
What are the most common causes of impetigo?
Staph aureus is #1
Strep pyogenes is #2
Describe the effects of GAS (S. pyogenes) in terms of Pyogenic, Toxigenic, Immunologic
Pyogenic: pharyngitis, cellulitis, impetigo, erysipelas
Toxigenic: TSS, scarlet fever, necrotizing fasciitis
Immunologic: rheumatic fever, glomerulonephritis
Clinical presentation and characteristics of rheumatic fever
This is an immunologic response to S. pyogenes. Ab's to M protein cross-react with heart causing damage. Has Aschoff bodies, elevate ASO titers. Follow Strep pharyngitis. Remeber JONES criteria: J: joints–polyarthritis O: (heart)–carditis N: Nodules (subcutaneous) E: Erythema marginatum S: Sydenham chorea
Describe features of Scarlet fever
This is a toxigenic response to S pyogenes
Blanching, sandpaper-like rash on body, strawberry tongue, circumoral pallor all in the context of GAS pharyngitis
What kind of infection generally precedes glomerulonephritis caused by GAS?
Impetigo
Though, can come after pharyngitis, cellulitis, erysipelas
Patient in Mississippi or Ohio river valley with history of cleaning bird cages or exploring caves has high risk of what infection?
Histoplasma capsulatum, a fungus commonly found in guano and soil where bird or bat droppings are
Macrophage filled with Histoplasma is common
Remember: Histo Hides in macrophages
Waterhouse-Friederichsen syndrome
Complication of meningococcemia (N. meningitidis) that may involve adrenal gland destruction, DIC (purpuric skin lesions), shock, death.
Most common cause of CAP and meningitis?
Strep pneumoniae
What are the most common causes of infective diarrhea in adults and kids?
Kids: viral
Adults: bacterial–Campylobacter, Salmonella, Shigella, E. coli
Most common causes of acute and subacute bacterial endocarditis
Acute: Staph aureus
Subacute: Strep viridans
Patient gardening and gets a thorn prick. Lesions develop that when cultured at 24 degrees C produce branching hyphae. Biopsy specimen showed round or cigar-shaped budding yeast. Dx? Clinical presentation?
Sporothrix schenckii: lives on vegetation,
Clinical: Pustules, ulcers, subcutaneous nodules along lymphatics (ascending lymphangitis)
Name the thermally dimorphic fungi and what dimorphic means
Dimorphic: mold at ambient temperature, yeast at body temp (cold=mold, heat=yeast)
Sporothrix schenkii–gardner’s disease, ascending lymphangitis
Coccidioides immitis–SW states, pneumonia and meningitis, biopsy shows thick-walled spherules (not yeast)
Histoplasma capsulatum–hides in macrophages, river valleys, guano
Blastomyces dermatitidis–river valleys and great lakes, broad based bud
Paracoccidioides brasiliensis–budding yeast with captain’s wheel formation, central and south america
Features of Coccidioides immitis
SW USA, mold in the soil
Infects the lungs: flu-like, cough, erythema nodosum
Disseminated: skin, bones, lungs
Hyphae at 25C, thick-walled spherules with endospores on biopsy
What are the two fungal infections in Ohio and Mississippi river valleys? How are they different?
Histoplasma capsulatum: bird droppings and soil, in macrophages
Blastomyces dermatitidis: great lakes region, soil, doubly refractile wall and broad based buds
What fungus is not dimorphic, has septate hyphae, and has V branching?
Aspergillus
What microbe causes meningoencephalitis, is heavily encapsulated, found in soil and pigeon droppings, is highlighted by India Ink or Mucicarmine, agglutinates in latex agglutination test? What is the characteristic lesion in the brain?
Cryptococcus neoformans
Soap-bubble lesions in the brain
Commonly causes meningitis in AIDS
What fungus presents with 90 degree branching and nonseptate hyphae and what is the classic presentation?
Mucor, Rhizopus
Paranasal infection in diabetic ketoacidosis patient
Metronidazole MOA and use
Inhibits nucleic acid synthesis by disrupting the DNA of microbial cells. Only functional when reduced by anaerobic cells and therefore has little effect on human or aerobic bacteria
Use: Bacterial vaginosis, Trichomoniasis, Giardiasis, C. difficile, E histolytica
Female patient has thin, off-white vaginal discharge with fishy odor but no signs of inflammation. What are the lab findings, Dx, and Tx?
Clue cells, + whiff test (amine odor with KOH)
Bacterial Vaginosis–Gardnerella vaginalis
Metronidazole or Clindamycin
Female patient has thin, yellow-green malodorous frothy discharge with inflammation. What are the lab findings, Dx, and Tx?
Motile trichomonads best seen under wet mount (saline microscopy)
Trichomonas vaginalis
May also show strawberry cervix
Metronidazole
Female patient has thick, cottage cheese vaginal discharge and inflammation. What are lab findings, Dx, Tx?
Pseudohyphae
Candida albicans
Fluconazole
Compare presentation of UTI, PID, and Vaginitis and some causes.
UTI: burning, frequency, urgency on urination, suprapubic tenderness, but no vaginal discharge, E. coli, S saprophyticus
Vaginitis: discharge, may have some urinary Sx, itching, but no adnexal or cervical motion tenderness, caused by Gardnerella, Trichomonas, Candida
PID: discharge from the cervical os, N. gonorrhea and C. trachomatis, cervical motion tenderness
What type of virus is the most common cause of viral meningitis?
Enteroviruses:
Coxsackievirus, Echovirus, Poliovirus
How does the presentation of viral meningitis differ from bacterial or fungal?
Viral tends to be less severe and lack focal neurological deficits, seizures, and altered mental status
But will include fever, headache, vomiting, neck stiffness
What is Coronavirus a common cause of?
Cold Sx
What type of virus is West Nile Virus and how might it present?
Flavivirus transmitted by Culex mosquito in the summer
Causes: neuroinvasive disease causing encephalitis, meningitis, flaccid paralysis
What complication can occur to an elderly patient with dehydration and recent intubation?
This combination can lead to infection of the parotid gland by Staph aureus. Sx include firm tenderness pre or post auricular and down into the jaw. Confirmed by elevated amylase without elevated lipase, and ultrasound showing inflamed ducts.
What is lysogenization?
Process by which a bacteriophage introduces DNA that changes the phenotype of the bacteria.
Example is with Corynebacterium diptheriae that gets its ability to produce toxin from a bacteriophage.
What is the major virulence factor for S. pneumoniae?
Capsule
What is an important virulence factor for H flu?
PRP Capsule
Allows it to escape destruction by humoral immunity
What virulence factor of TB allows it to cause disease and what are its specific functions?
Cord Factor
Allows the organism to grow in long serpentine cords
It inactivates neutrophils, damages mitochondria, and induces release of TNF
Pyrimethamine
Antiparasitic drug used to treat malaria and toxoplasmosis
HIV patient not taking meds presents with 2 weeks of lethargy, seizures, and found to have multiple ring-enhancing lesions in brain. Dx? Tx?
Toxoplasmosis
Pyrimethamine and Sulfadiazine or Clindamycin
Second most common cause of ring-enhancing brain lesions in HIV is Primary CNS Lymphoma
Which bacteria are obligate intracellular?
Rickettsia, Chlamydia, Coxiella
Which bacteria are encapsulated?
(Please SHINE my SKiS) Pseudomonas aeruginosa Strep pneumoniae Haemophilus influenza type B Neisseria meningitidis E. coli Salmonella Klebsiella pneumoniae GBS
Which bacteria are facultative intracellular?
(Some Nasty Bugs May Live FacultativeLY) Salmonella Neisseria Brucella Mycobacterium Listeria Francisella Legionella Yersinia pestis
Urease positive bacteria
(Pee CHUNKSS) Proteus Cryptococcus H pylori Ureaplasma Nocardia Klebsiella S epidermidis S saprophyticus Urease hydrolizes urea releasing ammonia and CO2 which raise the pH and can lead to struvite crystals (ammonium magnesium phosphate)
What bug causes contact lens-associated keratitis?
P aeruginosa
What is protein A?
Expressed by S aureus
Binds Fc region of IgG. Prevents opsonization and phagocytosis
What is IgA protease?
Virulence factor
Enzyme that cleaves IgA in order to allow colonization of mucosa
S pneumo, H flu, Neisseria
What is M protein?
Virulence factor of GAS
Prevents phagocytosis, possible reason for rheumatic fever
What toxins are transferred to bacteria by transduction?
(ABCD'S) GAS erythrogenic toxin Botulinum toxin Cholera toxin Diphtheria toxin Shiga toxin
What spore forming bacteria causes food poisoning besides C. botulinum?
Bacillus cereus
What spore forming bacteria causes Gas gangrene?
Clostridium perfringens
What are the two groups of bacteria that form spores?
Bacillus
Clostridium
What are some of the virulence factors of Neisseria meningitidis?
Capsule–prevents phagocytosis
LOS–responsible for most of the systemic Sx including sepsis and the bilateral cortical adrenal hemorrhages seen in Waterhouse-Friedrichsen syndrome
What bacteria produces TSST-1 and what does the toxin do?
Staph aureus causes toxic shock syndrome by binding to MHC II and TCR causing overwhelming release of IL-1,2, IFN-gamma, TNF-alpha leading to shock
TSS: fever, rash, shock, vomiting, desquamation, end-organ failure, increased liver enzymes and bili.
What bacteria releases exotoxin A and what does it do? What other toxin does it release?
Strep pyogenes
Similar effect as Staph aureus toxic shock protein leading to toxic shock syndrome by causing a cytokine storm
Also releases streptolysin O which is a protein that degrades cell membranes and lyses RBC’s making it beta hemolytic
What is the toxin released by C perfringens and what does it do?
Alpha toxin: a phospholipase that degrades tissue and cell membranes allowing for myonecrosis and hemolysis leading to gas gangrene
Also called Lecithinase or phospholipase C
What is endotoxin and what does it do?
Outer membrane of G(-) bacteria, heat stable
O antigen + core polysaccharide + Lipid A (toxic part)
Released upon cell lysis or when blebs come off membrane
3 main effects: it activates:
Macrophages: IL1,6, TNF-alpha, NO release causing fever and hypotension
Complement: C3a, C5a release causing histamine release, hypotension, edema, neutrophil chemotaxis
Tissue Factor: DIC
What bacteria?
G(+) cocci in clusters, catalase (+), Coagulase (+)
Staph aureus
What bacteria?
G(+) cocci in clusters, catalase (+), Coagulase (-)
Two options:
S epidermidis: Novobiocin sensitive
S saprophyticus: Novobiocin resistant
What bacteria?
G(+) cocci, catalase (+), beta hemolytic
Besides the Strep bac that are beta hemolytic, Staph aureus is also
Which Staph makes a fibrin clot around itself and how?
Staph aureus
Uses coagulase
Describe Staph aureus food poisoning
Ingestion of pre-formed toxin that is heat stable and therefore not inactivated by cooking
Causes rapid onset nonbloody diarrhea and emesis
Mechanism of resistance in MRSA
Altered PBP
Patient gets pneumonia after an infection with the flu. What is likely bacterial cause?
Staph aureus
Which bacteria forms a protein that binds to the Fc region of IgG effectively camouflaging itself?
Staph aureus
Protein A
What is the second most common cause of uncomplicated UTI in young women?
Staph saprophyticus
Features of Strep pneumoniae
G(+), lancet shaped diplococci Encapsulated (no virulence without) IgA protease Alpha hemolytic Optochin sensitive Most common cause of Meningitis, Otitis media, Pneumonia, Sinusitis Rusty sputum Sepsis in sickle cell and those with splenectomy
Which Strep viridans bacteria most commonly causes subacute endocarditis and why?
Strep sanguinis
Produces dextran which binds to fibrin-platelet aggregates on damaged heart valves
What group of bacteria is S. gallolyticus and what should be assumed if it is found in the blood?
Strep bovis
Colonizes the gut
Bovis in the Blood = Cancer in the Colon
What is unique about the outside of B anthracis?
The only bacterium with a polypeptide capsule containing D-glutamate
What bacteria causes a painless papule that becomes an ulcer with a black eschar?
Bacillus anthracis
Lesion is painless but necrotic
Describe disease presentation of inhaled anthrax
flu-like Sx that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, and shock
known as woolsorter’s disease
What bacteria is to blame for nausea and vomiting 1-5 hr after ingesting rice or pasta?
Bacillus cereus
Reheated rice syndrome
Spores survive cooking rice and keeping it warm causes germination of spores forming the enterotoxin
Also has a diarrheal type causing watery, nonbloody diarrhea
Why can’t babies have honey?
Babies get floppy baby syndrome from honey that contains C botulinum spores
Leads to descending floppy paralysis
Treated with antitoxin
How are Nocardia and Actinomyces treated?
Treatment is a SNAP
Sulfonamides for Nocardia
Actinomyces is Penicillin
Disease manifestations of Nocardia and Actinomyces
Nocardia: immune compromised patients, cutaneous infections after trauma, pulmonary infection mimicing TB but neg PPD
Actinomyces: normal oral flora, oral/facial abscesses with yellow sulfur granules, can cause PID with IUD’s
What are the Sx of TB?
Fever, night sweats, weight loss, cough, hemoptysis
What are the virulence factors of TB?
Cord factor: creates serpentine cords in virulent M tuberculosis, inhibits macrophage maturation, induces TNF-alpha release
Sulfatides inhibit phagolysosomal fusion
Describe two forms of Hansen disease and treatment
Caused by Mycobacterium leprae, glove and stocking loss of sensation
Lepromatous: diffusely over skin, leonine faciea, communicable, low cell-mediated immunity so mount primarily a Th2 humoral response, can be lethal
Tuberculoid: limited to few plaques, high cell-mediated immunity with largely Th1-type response
Treatment: dapsone and rifampin for tuberculoid, add clofazimine for lepromatous
How might the presentation of a primary vs reactivation of HSV-1 be different?
Primary infection: ages 6mo-5yr most often, causes gingivostomatitis including painful ulcers on the gums, tongue, palate, lips, and oropharynx; also has systemic Sx of fever and malaise; resolves in 1-2 weeks, pain of the ulcers often leads to dehydration leading to hospitalization
Reactivation is generally much more mild and only involves the lips and is often unilateral
G(-) bacillis grows white on MacConkey agar, oxidase (+), Dx?
Pseudomonas
Lab diagnostic features for Pseudomonas
G(-), Bacillus, Non lactose fermentation, Oxidase (+)
What are the G(-) bacilli bacteria that are lactose fermentors?
Fast: Klebsiella, E. coli, Enterobacter
Slow: Citrobacter, Serratia
What are the G(-) bacilli bacteria that do not ferment lactose and are oxidase (-)?
H2S producing on TSI agar: Salmonella, Proteus
Non H2S: Shigella, Yersinia
What are the tests to differentiate the G(-) diplococci?
All are aerobic and oxidase (+), check Maltose utilization:
(+): N meningitidis
(-): N gonorrhoeae, Moraxella
How are the G(-) comma shaped rods that are motile differentiated?
All are oxidase (+)
Campylobacter: grows in 42C
Vibrio cholerae: Grows in alkaline media
H. pylori: urease producing
How are E. coli and Enterococcus differentiated?
E. coli is indole (+) meaning it can convert tryptophan to indole
What are two common causes of UTIs in patients with Foley catheters?
Proteus and Pseudomonas
What is an IGRA?
IFN-gamma Release Assay
Tests for latent TB infection by exposing patient’s T-cells to TB antigens and looking for a response which would include release of IFN-gamma which activates macrophages and promotes development of Th1 cells
Which ulcerating STD has multiple deep painful ulcers with a base that may be gray to yellow? What would be seen on microscopy?
Haemophilus ducreyi causing Chancroid disease
Microscopy would show clumping in long parallel strands like a school of fish
What ulcerating STD has multiple, painful, grouped ulcers that are shallow and erythematous? What would be seen on microscopy?
Herpes Simplex type 1 or 2 causing genital herpes
Microscopy would show Multinucleated giant cells and intranuclear inclusions (Cowdry type A)
What diseases cause painless ulcers on the genitals?
Klebsiella granulomatis
Treponema pallidum
Chlamydia trachomatis
What ulcerating STD has extensive and progressive painless ulcerative lesions without LAD and shows G(-) intracytoplasmic cysts called Donovan bodies?
Klebsiella granulomatis causing Granuloma inguinale (donovanosis)
What ulcerating STD has painless, single, well-circumscribed ulcers with a clean base that clear within a week or two and if not treated will lead to a rash? What is seen on microscopy?
Syphilis caused by Treponema pallidum
See thin, delicate, corkscrew organisms on darkfield microscopy
What ulcerating STD has painless small and shallow ulcers with large, painful inguinal lymph nodes (buboes), and what would be seen on microscopy?
Lymphogranuloma venereum caused by Chlamydia trachomatis
Microscopy would show intracytoplasmic chlamydial inclusion bodies in epithelial cells and leukocytes
What is lymphogranuloma venereum?
Caused by certain strains of Chlamydia
Starts with painless ulcerations of the genitals that progress to painful and swollen lymph nodes (buboes), chlamydial inclusion bodies seen in the cytoplasm of cells
What is allergic bronchopulmonary aspergillosis?
Patients with asthma or COPD who are chronically on steroids to control Sx can have an aspergillus infection in the bronchi that they have an allergic reaction to. They will have elevated IgE and Eosinophils, transient and recurrent pulmonary infiltrates, and proximal bronchiectasis
What are cold agglutinins and what diseases can they accompany?
Cold agglutinins are antibodies that cross react with RBC’s surface antigens but only cause agglutination at cold temperatures, can lead to transient anemia in patients.
Associated with Mycoplasma pneumoniae, EBV, hematologic malignancies
Difference between polysaccharide vaccine and conjugated vaccine for pneumococcus
The conjugated vaccine combines a polysaccharide capsular antigen with a protein so it can be presented to T cells and induce a stronger and longer lasting immune response that is more protective for the elderly, infants, and immune compromised
What is haptoglobin and how is it used as a blood value?
Haptoglobin binds free Hb and to prevent its oxidative action from causing damage. The complex is then removed by the reticuloendothelial system/spleen
Intravascular hemolytic anemia releases Hb into the blood and haptoglobin binds it and its levels are then reduced. If the hemolysis is extravascular, theoretically the haptoglobin levels will not be reduced though other signs like elevated bilirubin will be present
What disease is caused by Borrelia burgdorferi?
Lyme disease
A spirochete bacteria
What is Babesiosis?
Caused by Babesia microti a parasite that infects RBC’s that is spread by the ixodes tick
Causes acute febrile illness, thrombocytopenia, hemolytic anemia, abnormal liver tests, and cross-shaped intraerythrocytic inclusions
Patients without a spleen are at high risk of pulmonary complications such as ARDS
What disease is known for ring-shaped erythrocyte inclusions?
Malaria
Patients without a spleen are at increased risk for what kind of bacterial infections and what vaccines are they given?
Encapsulated bacteria
S pneumoniae
N meningitidia
H flu
What is beta galactosidase?
Enzyme used by E. coli to digest lactose into glucose and galactose
Differentiate the Neisseria species based on fermentation of sugar
MeninGococci (has an M and G) ferment Maltose and Glucose
Gonococci (only a G) only Glucose
What is Fitz-Hugh–Curtis Syndrome?
Associated with N. gonorrhea or C. trachomatis infections in women where the microbes have spread from the reproductive tract to Glisson’s capsule around the liver and causing adhesions around the liver that cause RUQ pain that is worse with breathing, coughing, and laughing.
How are N. gonorrhoeae and N meningitidis different?
N. gonorrhoeae: no capsule, no maltose, no vaccine, sexually transmitted, PID, septic arthritis, Fitz-Hugh–Curtis syndrome
N meningitidis: capsule, maltose fermentation, vaccine, respiratory or oral secretion transmission, causes meningococcemia with petechial rash and gangrene of toes and Waterhouse-Friderichsen syndrome
Haemophilus influenzae characteristics
G(-) coccobacilliary rod
Aerosol transmission
Nontypeable strains (unencapsulated) most common cause of mucosal infections (otitis media, conjunctivitis, bronchitis)
Produces IgA protease
Chocolate agar growth–factor V and X needed
Causes epiglottitis, Meningitis, Otitis media, Pneumonia
Vaccine exists
Does not cause the flu
Treated with amoxicillin for mucosal, ceftriaxone for meningitis, rifampin for prophylaxis
What is the best stain for Legionella?
Silver stain
What media does Legionella grow on?
Charcoal yeast extract with iron and cysteine
What is Pontiac fever?
mild flu-like syndrome caused by Legionella
Legionnaire’s disease
Caused by Legionella
Severe pneumonia often unilateral and lobar, fever, GI and CNS Sx
Common in smokers and those with chronic lung disease
How is Legionella spread?
Through aerosol transmission from AC units or hot water tanks
No person to person transmission
What is the cause of hot tub folliculitis?
Pseudomonas aeruginosa
Ecthyma gangrenosum
Rapidly progressive necrotic cutaneous lesion caused by Pseudomonas in immunocompromised patients
Characteristics of Pseudomonas aeruginosa
Aerobic, motile, G(-) rod, non lactose fermenting, oxidase (+) Produces pyocyanin (blue-green pigment) Grape-like odor Produces endotoxin, exotoxin A (EF-2 inactivation), phospholipase C, pyocyanin (produces ROS)
What is Pseudomonas associated with?
(PSEUDOMONAS) Pneumonia Sepsis Ecthyma gangrenosum UTI's Diabetes, drug use Osteomyelitis (puncture wounds) Mucoid polysaccharide capsule Otitis externa Nosocomial infections (catheters) Exotoxin A Skin infections (hot tub folliculitis)
What are the common virulence factors of E. coli?
Fimbriae (P): cystitis and pyelonephritis
K capsule: pneumonia, neonatal meningitis
LPS endotoxin: septic shock
What are the most common types of E. coli?
EIEC: invasive, dysentery, Sx like Shigella
ETEC: heat labile and stable enterotoxins cause traveler’s diarrhea (watery)
EPEC: No toxin, adheres and flattens villi decreasing absorption, diarrhea in pediatric patients
EHEC: undercooked meat and raw leafy vegetables, Shiga-like toxin causing dysentery, UHS–microthrombi form on damaged endothelium causing mechanical hemolysis with schistocytes, platelet consumption, and decreased renal blood flow, does not ferment sorbitol like other strains
Characteristics of Klebsiella
G(-) rod, normal flora, causes lobar pneumonia with abscesses in alcoholics and diabetics who aspirate
Very mucoid colonies because of abundant capsule
Dark red “currant jelly” sputum
Causes nosocomial UTI’s
What pneumonia causing organism produces currant jelly sputum?
Klebsiella
What bacterial infection is a common antecedent to Guillain-Barre syndrome and reactive arthritis?
Campylobacter jejuni
Characteristics of Campylobacter jejuni
G(-), comma or S shaped with polar flagella, oxidase (+), grows at 42C
Causes bloody diarrhea in kids
Fecal-oral transmission, undercooked poultry or meat, unpasteurized milk
Common antecedent to Guillain-Barre syndrome and reactive arthritis
What bug causes Typhoid fever? Sx of Typhoid?
Salmonella typhi
Rose spots on abdomen, constipation, abd pain, fever, headache
An enteric fever spread through fecal oral
Remember Typhoid Mary
What two bacteria invade the GI tract via M cells of Peyer patches?
Salmonella
Shigella
How are Salmonella and Shigella same/different?
Salmonella is unique in that it: spreads hematogenously, produces H2S, has flagella, antibiotics prolong duration of fecal excretion and are not indicated in strains other than typhi
Shigella: cell to cell spread, no H2S, no flagella, low inoculum, antibiotics shorten fecal excretion, bloody diarrhea, invasion is key to pathogenicity
When does Shigella typhi develop a carrier state?
When it colonizes the gall bladder
How is Salmonella (except for typhi) spread? Tx? Major Sx?
Poultry, eggs, pets, turtles
Antibiotics not indicated
Gastroenteritis generally from these strains and not typhi
Characteristics of Vibrio cholerae
G(-), flagellated, comma shape, oxidase (+)
Rice-water stools from increased cAMP
Large inoculum
Prompt oral rehydration necessary
What bacteria can cause pseudoappendicitis?
Yersinia enterocolitica
Characteristics of Yersinia enterocolitica
G(-) rod, usually from pet feces, contaminated milk, pork
Causes acute diarrhea or pseudoappendicitis
What bacteria is triple positive and requires triple treatment?
H. pylori
catalase (+), oxidase (+), urease (+)
Therapy: Amoxicillin (or metronidazole) + Clarithromycin + PPI
How is an H. pylori infection diagnosed?
Urea breath test or
Fecal antigen test
Describe features of an H pylori infection including where it colonizes, what it causes, and what it is a risk factor for.
Urease produces ammonia and an alkaline environment which helps it survive in the antrum of the stomach
Causes gastritis and peptic ulcers especially in the duodenum
Risk factor for: PUD, gastric adenocarcinoma, MALT lymphoma
Leptospirosis
Caused by Leptospira interrogans
Spirochete found in water contaminated by animal urine
Flu-like Sx, myalgia (classically in calves), jaundice, photophobia, red conjunctiva without exudate
Prevalent among surfers in tropics (Hawaii)
Describe Lyme disease
Borrelia burgdorferi from Ixodes tick, natural reservoir is the mouse
Stage 1: early localized, erythema migrans, flu-like
Stage 2: early disseminated, carditis, AV block, bell’s palsy, migratory myalgias, transient arthritis
Stage 3: late disseminated, encephalopathies, chronic arthritis
Remember: Key Lyme pie to the FACE Facial nerve palsy Arthritis Cardiac block Erythema migrans
What is erythema migrans?
Pathognomonic rash of Berrelia infection associated with Lyme disease
Bull’s eye rash/target lesion that is good enough to have a diagnosis without labs
Describe primary syphilis
Localized
Painless chancre
Dx with darkfield microscopy
VDRL (+) in about 80%
Describe secondary syphilis
Disseminated disease with constitutional Sx
Maculopapular rash including palms and soles, condyloma lata, LAD, hair loss
Dx darkfield microscopy
VDRL/RPR nonspecific, follow with FTA-ABS
Can become latent after this
Tertiary syphilis
Gummas, aortitis, neurosyphilis, Argyll Robertson pupil (accommodates, but doesn’t react to light), braod based ataxia, (+) Romberg, charcot joint, stroke without HTN
For neurosyphilis: test CSF with VRDL, FTA-ABS and PCR
Congenital syphilis
Usually transferred after first trimester through placenta
Kids have rhagades (linear scars at angle of mouth), snuffles (nasal discharge), saddle nose, Hutchinson teeth, mulberry molars, short maxilla, saber shins, CN VIII deafness
Jarisch-Herxheimer reaction
Flu-like syndrome after antibiotic administration caused by killed bacteria, usually spirochetes, releasing toxins
How is Anaplasma transmitted?
Ixodes tick
What bacteria causes cat scratch disease?
Bartonella
Cause and source of relapsing fever
Borrelia recurrentis
Louse bourne
Patient has undulating fever. Likely Dx? Source?
Brucellosis, unpasteurized dairy
What bug causes bloody diarrhea after exposure to the feces of infected pets or animals?
Campylobacter
What is Psittacosis?
Zoonotic disease caused by parrots and other birds
Caused by Chlamydophila psittaci
What is Q fever?
Caused by Coxiella burnetii
Infection from aerosols of cattle/sheep amniotic fluid
Presents as pneumonia, has no rash and no vector
Is most common cause of culture negative endocarditis
What disease is transferred by the tick Amblyomma (Lone Star Tick)
Ehrlichiosis from
Ehrlichia chaffeensis
What disease comes from water contaminated with animal urine?
Leptospirosis
What bug causes cellulitis, osteomyelitis after an animal bite?
Pasteurella multocida
How is epidemic typhus spread?
Human to Human via body louse
Rickettsia prowazekii
What disease is caused by Rickettsia rickettsii?
Rocky Mountain Spotted Fever
Dermacentor (dog tick)
How is endemic typhus spread?
Fleas
Rickettsia typhi
Female patient with vaginal discharge found to have Clue cells on microscopy, Dx? Tx?
Clue cells appear with gardnerella vaginosis
They have a stippled appearance along outer margine
metronidazole, or clindamycin
What is the treatment for all Rickettsial diseases?
Doxycycline
Which diseases cause a rash on the palms and soles?
Coxsackievirus A
Rocky Mountain Spotted Fever
Secondary Syphilis
Features of Rocky Mountain Spotted Fever
Rickettsia rickettsii
Dermacentor tick vector
Primarily in the south atlantic states like NC
Rash starts on wrists and ankles and spreads to trunk, palms, and soles
Triad: headache, fever, rash
Characteristics of Typhus
Endemic (fleas): R. typhi
Epidemic (human body louse): R. prowazekii
Rash starts centrally and spreads out, sparing palms and soles (opposite of RMSF)
What diseases have morulae (mulberry-like inclusions) in cytoplasm?
Ehrlichia: inclusions in monocytes
Anaplasmosis: inclusions in granulocytes
Morulae are like smell berries inside these cells
Both diseases are spread by ticks
General characteristics of Chlamydia infection
Obligate intracellular, mucosal infections
Elementary body: small and dense, enters cell by endocytosis and transforms into reticulate body
Reticulate body: replicates in cell by fission, reorganizes into elementary body
C trachomatis: reactive arthritis, follicular conjunctivitis, urethritis, PID
C pneumoniae and psittaci: cause atypical pneumonia by aerosol transmission
Treatment: azithromycin or doxycycline, beta-lactams not very effective
Giemsa or fluorescent antibody detection
Serotypes of C trachomatis
A, B, C: cause chronic infection and blindness from follicular conjunctivitis
D-K: PID, ectopic pregnancy, neonatal pneumonia
L1, L2, L3: Lymphogranuloma venereum–small painless ulcers on genitals becoming painful swollen inguinal lymph nodes called buboes, treat with doxycycline
What causes walking pneumonia?
Mycoplasma pneumoniae
Has no cell wall so doesn’t gram stain
Has sterols in membrane for stability
X-ray looks worse than patient
High cold agglutinin titers
Common outbreaks in prisons and military recruits
Treatment: macrolides, doxy, fluoroquinolone
Presentation of an infant who ingested C botulinum
Infant botulism: spores are ingested and toxins are produced later in the gut, constipation precedes NM Sx by days to weeks, mild weakness, lethargy, poor feeding, loss of muscle tone possible, weakened suck, swallowing, crying
Adults: ingest pre-formed toxin causing sever Sx
How do liver enzymes compare between an acute viral hepatitis vs a more chronic condition?
Levels tend to me in the thousands for an acute viral infection and in the hundreds for a chronic condition
What is Fanconi’s syndrome?
Condition affecting the proximal tubules of the kidney where amino acids, proteins, glucose, uric acid, phosphate, bicarb are not absorbed and lost in the urine.
Causes renal tubule acidosis, polyuria, polydipsia, dehydration, loss of phosphate leading to rickets and osteomalacia
What is Hartnup disease?
Similar to Fanconi’s except more specific to inhibited transport of neutral amino acids in the intestines and proximal tubules of the kidneys, specifically tryptophan leading to low levels of Niacin among other things causing low nicotinamide needed for NAD+
Elevated amino acids in the urine
What diseases/conditions are caused my malassezia furfur?
Tinea versicolor (pityriasis) , dandruff, Seborrhoeic dermatitis Many skin diseases are caused by M. globosa
What are the most common Sx of a candida infection in immune compromised patients?
Right sided endocarditis
Renal abscesses
Pneumonia
Esophagitis
What signs might indicate that a UTI has become pyelonephritis?
Fever, Chills, Flank pain
Many UTI’s can be asymptomatic
What is the preferred method of preventing GBS leading to neonatal sepsis, meningitis, pneumonia?
Universal testing of mothers at 35-37 weeks gestation for presence of GBS in perianal/genital region. If positive, administer intrapartum penicillin or ampicillin
What are the classic foods associated with S. aureus food poisoning leading to short onset of Sx from pre-formed enterotoxin?
Classically mayonnaise containing foods like potato or macaroni salad
Also: poultry, eggs, meat, tuna/egg/chicken/potato/macaroni salad, cream pastries, milk and dairy
Often at picnics and BBQ’s because the food is left sitting out for a while allowing the formation of the toxins
What types of food poisoning produce their exotoxins after being ingested instead of before like S aureus?
ETEC, EHEC, Vibrio cholerae, Shigella
Name some bacteria that invade the gut mucosa
EIEC, Salmonella, Shigella, Yersinia, Campylobacter
All can cause bloody or inflammatory diarrhea
What enteritis causing parasite causes bloody diarrhea and liver abscesses?
Entamoeba histolytica
Sx of giardia
Non-bloody, putrid smelling, frothy diarrhea and bloating after drinking bad water
What are the diseases caused by exotoxin from S aureus?
Toxic shock syndrome
Staph scalded skin syndrome
Gastroenteritis
What is a germ tube test?
Inoculate serum at 37C with fungus for 3 hours and look for budding yeast with growing pseudohyphae or germ tubes
Test for Candida albicans, other Candida species will not form germ tubes
Immune compromised patient has crackles in lungs and CXR shows hilar LAD. Bronchoscopy specimen shows mucicarmine staining budding yeast with large capsule. Dx?
Cryptococcus neoformans
Very common cause of pneumonia and meningitis in immune compromised patients
Known for staining with India Ink (CSF) or Mucicarmine (pulmonary lavage) and having a thick capsule
Found in soil and pigeon droppings
Word for painful swallowing
Odynophagia
How does the diptheria toxin work?
It is an AB toxin that inhibits protein synthesis by ADP ribosylation of protein Elongation Factor-2
If it goes systemic, it likes heart and brain tissue causing myocarditis and neurological toxicity
How does Corynebacterium diptheriae appear under microscope?
Non-motile, unencapsulated, G(+) rods
In clumps resembling chinese characters like V’s or Y’s
Cytoplasm contains granules that stain with aniline dyes (like methylene blue)
Consumption of raw oysters leads to infection of what bacteria?
Vibrio species of several kinds
HUS from EHEC most commonly affects what age group?
Rare syndrome usually affecting kids under 10
Can come on after treatment with antibiotics
Are Mucor and Rhizopus septate or not?
Usually non septate hyphae with 90 degree branching
Diabetic patient has black eschar on turbinates in nose, what is likely treatment?
This is a common sign of Mucormycosis and is treated with amphotericin B
How are aspergillus and Mucor different in the patients they infect in the sinus?
Mucor is generally diabetics, thought to be because of ability to use ketones to survive in acidotic and hyperglycemic environment
Aspergillus more common in neutropenic patients
How are local and systemic mycoses treated?
Local: fluconazole or itraconazole
Systemic: amphotericin B
Erythema Nodosum
Think: Red Nodules on shins
Inflammatory condition with inflammation of the fat cells under the skin resulting in tender red nodules
Caused by lots of things including:
Strep in kids, Primary TB infection, Coccidioides, M. pneumo, Histoplasma, Yersinia, EBV, cat scratch
Which systemic mycoses can increase in prevalence after an earthquake or other natural event that puts dust in the air?
Coccidioides
What are desert bumps and desert rheumatism?
Sx of Cocci including erythema nodosum and arthralgias
Tinea is the clinical name for what? What are the different genera or species of this group? Microscopy?
Tinea is word for dermatophytes
Microsporum, Trichophyton, Epidermophyton
Branching septate hyphae visible on KOH with blue fungal stain
Name the different cutaneous mycoses and characteristics
Tinea Capitis: head, scalp, LAD, alopecia, scaling
Tinea corporis: torso, scaling rings with central clearing, acquired from cat or dog
Tinea cruris: Inguinal, often no central clearing
Tinea pedis: interdigital type most common, moccasin type, vesicular type
Tiniea unguium: onychomycosis on nails
Describe Pityriasis
Tinea versicolor
Malassezia spp., yeast-like fungus and not a dermatophyte despite Tinea name
Feeds on lipids producing acid that damages melanocytes and causes hypopigmentation or pink patches
Any time of year, but especially summer
Spaghetti and meatballs on microscopy
Treat with selenium sulfide or other oral antifungal
Morphology of Candida albicans
Dimorphic:
pseudohyphae and budding yeast at 20C, germ tubes at 37C
Candida treatment
Vaginal: topical azole
Oral/esophageal: fluconazole, caspofungin, nystatin
Systemic: fluconazole, caspofungin, amphotericin B
Aspergillus fumigatus characteristics
Septate hyphae, 45 degree branching, Conidia at the end of conidiophores
Invasive aspergillosis in immune compromised
Aspergillomas in pre-existing lung cavities like after TB infection
Allergic Bronchopulmonary Aspergillosis: hypersensitivity to fungus in asthma and COPD causing bronchiectasis and eosinophilia
What fungal disease is associated with latex agglutination?
Cryptococcus neoformans
Test detects polysaccharide capsular antigen
What bug causes a ground glass appearance on CXR and a diffuse interstitial pneumonia? Other features?
Pneumocystis jirovecii
Yeast-like fungus
Immune compromised most often
Disc-shaped yeast on methenamine silver stain of lung tissue
How is Pneumocystis jirovecii treated?
TMP-SMX, pentamidine, atovaquone
Dapsone for prophylaxis only
Lung biopsy or lavage shows disc shaped yeast on methenamine silver stain. Dx?
Pneumocystis jirovecii
Morphology and treatment of Sporothrix schenkii
Dimorphic: cigar shaped budding yeast that grows in branching hyphae with rosettes of conidia
Treatment: itraconazole or potassium iodide
Name and describe the three main protozoal GI infections
Giardia: bloating, flatulence, fatty diarrhea, Dx with multinucleated trophozoites or cysts in stool, treated with metronidazole
E. histolytica: bloody diarrhea and liver abscesses, RUQ pain, serology shows trophozoites with engulfed RBC’s or cysts with up to 4 nuclei, treat with metronidazole or iodoquinol
Cryptosporidium: severe diarrhea in AIDS, mild diarrhea in competent hosts, acid fast oocysts in stool
What disease can you get from swimming in fresh water lakes that is rapidly fatal from meningoencephalitis?
Naegleria fowleri (protozoa) Amoebas get into spinal cord Treat with amphotericin B, but low chance of survival
What disease causes a triad of Sx in neonates of chorioretinitis, hydrocephalus, intracranial calcifications?
Toxoplasma gondii
What disease causes ring-enhancing lesions when reactivated in AIDS? How is it treated? How is it transmitted?
Toxoplasma gondii
From cysts in meat or oocysts in cat feces
Crosses the placenta to fetus
Treat with sulfadiazine + pyrimethamine
What causes African sleeping sickness?
Trypanosoma brucei (a protozoa that has a single flagella that runs the length of the body)
Features of African Sleeping Sickness
Enlarged lymph nodes, recurring fever, somnolence, coma
Tsetse fly painful bite
Trypomastigote in the blood smear
Name the 4 types of malaria and general features of each
Plasmodium vivax/ovale: tertian–48 hours between fevers, have dormant form in liver, most common types, benign
Plasmodium falciparum: tertian, most severe and cause of death, irregular fever patterns, parasites in RBC’s occlude capillaries in brain, kidneys, lungs
Plasmodium malariae: quartan, no liver
Which malaria drug is a tissue schizonticide?
Primaquine
Which malaria forms infect the liver?
vivax and ovale
Drugs used for malaria
Chloroquine: blocks plasmodium heme synth
If resistant to above: mefloquine or atovaquone/proguanil
If life threatening: IV quinidine (test for G6PD deficiency)
For vivax/ovale: add primaquine for hypnozoites in liver
Describe Chagas disease
Trypanosoma cruzi, mostly South America, from kissing bug
Dilated cardiomyopathy with apical atrophy, megacolon, megaesophagus, Romana sign
Treated with Benznidazole or Nifurtimox
Remember trypanosomes have single long flagella running length of the body, same as in african sleeping disease
What is Romana sign?
Unilateral periorbital swelling characteristic of advanced Chagas disease
What disease comes from the bite of a sand fly? Features of disease?
Leishmaniasis: from gulf war, infects macrophages, treated with amphotericin B or Stibogluconate sodium
Visceral form: spiking fevers, HSM, pancytopenia
Cutaneous form: skin ulcers
Mucocutaneous form: involves skin and cartilage, severe deformation
Differentiate these rashes: Erythema Nodosum Erythema Multiforme Erythema Migrans Erythema Marginatum
Nodosum: subQ nodules, inflammation of fat cells under skin, LE; causes: cocci, cat scratch, yersinia, EBV, histoplasma, M. pneumo, TB, Strep
Multiforme: many presentations (including target form) and many causes including bacterial, cocci, herpes, others
Migrans: target lesion pathognomonic for Lyme disease
Marginatum: torso, inner part of limbs and extensor surfaces, rare presentation but associated with rheumatic fever (10%)
Young patient found to have anal puritis, Sx of an intestinal infection, and the tape test shows eggs. Dx? Transmission? Treatment?
Nematode infection
Dx: Enterobius vermicularis (pinworm)
Transmission: Fecal-oral
Tx: Bendazoles
What group of worms are round worms?
Nematodes
Patient has intestinal infection with a worm that obstructs the ileo-cecal valve. Dx? Transmission? Tx?
Nematode infection
Ascaris lumbricoides (giant roundworm)
Fecal-oral, eggs visible in feces with microscope
Bendazoles
What worm causes intestinal infection with vomiting, diarrhea, epigastric pain that can mimic PUD? Transmission? Tx?
Nematode infection
Strongyloides stercoralis (threadworm)
Larvae in soil penetrate skin
Ivermectin or Bendazoles
What worms are the hookworms? What are they known for?
Nematodes
Ancylostoma duodenale
Necator americanus
Known for causing anemia by sucking blood through the intestinal wall, cutaneous larva migrans
Transmission: larvae penetrate skin
Tx: Bendazoles, Pyrantel pamoate
Disease caused by Trichinella spiralis
Transmission, Sx, Tx
Nematode infection
Transmission: fecal-oral; undercooked pork
Intestinal infection, larvae enter blood stream and encyst in striated muscle cells causing inflammation. Trichinosis=fever, vomiting, nausea, periorbital edema, myalgia
Tx: bendazoles
Toxocara canis
Nematode infection
Visceral Larva migrans: fecal-oral, nematodes migrate through intestines to the heart, liver, CNS (seizures, coma)
Treated with Bendazoles
Onchocerca volvulus
Nematode infection
Female black fly transmission, river blindness, skin changes (black nodules), loss of elastic fibers
Tx: Ivermectin
Loa Loa
Nematode infection
Swelling in skin, worm in conjunctiva
Spread by Deer fly, Horse fly, Mango fly
Tx: Diethylcarbamazine
Wuchereria bancrofti
Nematode infection
Causes elephantiasis: worms invade lymph nodes and cause inflammation, takes 9 mo-1yr for Sx
Spread by female mosquito
Tx: Diethylcarbamazine
What are cestodes?
Tapeworms
Taenia solium
Cestode infection
Intestinal tape worm from encysted larvae in undercooked pork, treat: praziquantel
Cysticercosis/Neurocysticercosis: Ingestion eggs and human feces, lodge in the brain, can cause epileptic seizures, common in poorer countries and tropicals; Praziquantel for cysticercosis, Albendazole for neurocysticercosis
Diphyllobothrium latum
Cestode infection
Larvae from raw freshwater fish
Causes B12 deficiency and megaloblastic anemia
Praziquantel
What cestode causes Hydatid cysts in the liver?
Echinococcus granulosus
Ingestion of eggs from dog feces
Sheep are intermediate host
Treat with Albendazole
What are Trematodes?
Flukes
What worm has eggs with a lateral spine?
Trematode infection
Schistosoma mansoni
Liver and spleen enlargement, fibrosis, inflammation
Snails are host
What worm has eggs with a terminal spine?
Trematode infection Schistosoma haematobium Can cause squamous cell carcinoma of the bladder and pulmonary HTN Snails are host Treat with Praziquantel
What worm causes biliary tract inflammation leading to pigmented gallstones?
Clonochis sinensis
From undercooked fish
Also associated with cholangiocarcinoma
Treat with Praziquantel
General guide to treatments for worm infections
Roundworms: Bendazoles
Tapeworms and Flukes: Praziquantel
Parasite causing brain cysts and seizures
Taenia solium from undercooked pork
Parasite causing hematuria, squamous cell bladder cancer
Schistosoma haematobium
Terminal spine on egg
Parasite causingLiver hydatid cysts
Echinococcus granulosus
Parasite causing Microcytic anemia
Ancylostoma, Necator
Parasite causing Myalgias, periorbital edema
Trichinella spiralis
Parasite causing perianal puritis
Enterobius
Parasite causing portal hypertension
Schistosoma mansoni (lateral spine on egg) Schistosoma japonicum
Parasite causing Vit B12 deficiency
Diphyllobothrium latum
Scabies
Sarcoptes scabiei
Mites, burrow into stratum corneum causing puritis and burrows in web space of hands and feet
Common in kids and crowded places like jails, nursing homes
Treat with permethrin cream
Lice
Pediculus humanus/Phthirus pubis
Blood-sucking insects that prefer to live in clothing
Pink macules and papules in intertriginous areas
Can transmit: Rickettsia proazekii (typhus), Borrelia recurrentis (relapsing fever), Bartonella quintana (trench fever)
What does it mean when a virus in enveloped?
It has DNA inside a capsid that is covered with a lipid bilayer with proteins on it
Name the live attenuated viral vaccines
Small pox, Yellow fever, Rotavirus, chicken pox (VZV), Sabin Polio, MMR, Influenza intranasal
What live attenuated viral vaccine can be given to HIV patients who do not have Sx of immunodeficiency?
MMR
What are the killed viral vaccines?
Rabies, Influenza (injected), Salk polio, HAV
Difference between live and killed viral vaccines and immunity
Live: humoral and cell-mediated immunity
Killed: only humoral immunity
Of the DNA viruses, which are double stranded?
All are dsDNA (like our DNA) except for Parvovirus (think “part of a virus”)
Of the DNA viruses, which are linear?
All are linear except for papilloma, polyoma, and hepadnaviruses
Of the RNA viruses, which are single stranded?
All are ssRNA (like our RNA) except for Reovirus (think repeato-virus)
What are the + sensed RNA viruses?
Retrovirus, Togavirus, Flavivirus, Coronavirus, Hepevirus, Calicivirus, Picornavirus
Infectivity of naked viral genome
dsDNA and + strand ssRNA are infectious on their own
- strand ssRNA and dsRNA are not infectious
Where in the cell do viruses replicate?
DNA viruses: all in the nucleus except poxvirus
RNA viruses: all in the cytoplasm except influenza and retroviruses
What are the Naked viruses without envelopes?
DNA: (Think PAPP) Papilloma, Adeno, Parvo, Polyoma
RNA: (Think CPR) Calici, Picorna, Reo, Hepe
Where do viruses get their envelopes?
Generally from the plasma membrane when exiting the cell, except for herpesvirus that gets it from the nuclear envelope
What are the DNA viruses?
HHAPPPy viruses
Hepadna, Herpes, Adeno, Pox, Parvo, Papilloma, Polyoma
Herpesvirus
Linear Enveloped dsDNA
Includes: HSV-1&2, HHV-3 (VZV),4(EBV),5(CMV),6,7,8
Poxvirus
Linear Enveloped dsDNA
Largest DNA virus
Causes Smallpox, Cowpox, Molluscum Contagiosum–flesh colored papule with central umbilication
Hepadnavirus
Enveloped Partially dsDNA and circular
Hep B virus causing acute or chronic hepatitis
Adenovirus
Naked dsDNA linear Causes: febrile pharyngitis–sore throat acute hemorrhagic cystitis pneumonia conjunctivits
Papillomavirus
Naked dsDNA circular
Causes: HPV–warts (serotypes 1,2,6,11), CIN, cervical cancer (16,18)
Polyomavirus
Naked dsDNA circular
JC virus–progressive multifocal leukoencephalopathy (PML) in HIV
BK virus–transplant patients, commonly targets kidney
(JC=Junky Cerebrum, BK=Bad Kidney)
Parvovirus
Naked ssDNA linear (smallest DNA virus)
B19 virus: aplastic crisis in sickle cell; slapped cheek rash in kids (erythema infectiosum, or fifth disease)
Causes RBC destruction in fetus leading to hydrops fetalis and death
In adults causes pure RBC aplasia and RA-like Sx
HSV-1
Transmission, Clinical, Other
Transmission: respiratory, saliva
Clinical: gingivostomatitis, keratoconjunctivitis, herpes labialis, herpetic whitlow on finger, temporal lobe encephalitis
Other: most common cause of sporadic encephalitis
HSV-2
Transmission, Clinical, Other
Transmission: sexual contact, perinatal
Clinical: genital herpes, neonatal herpes
Other: latent in sacral ganglia, viral meningitis more common with HSV-2 than 1
VZV (HHV-3)
Transmission, Clinical, Other
Transmission: Respiratory
Clinical: chicken pox and shingles, encephalitis, pneumonia; most common complication of shingles is post-herpetic neuralgia
Other: latent in dorsal root or trigeminal ganglia
EBV (HHV-4)
Transmission, Clinical, Other
Transmission: respiratory, saliva–kissing disease
Clinical: Mononucleosis–fever, HSM, pharyngitis, LAD (especially post cervical); assoc. c lymphomas–Burkitt, nasopharyngeal carcinoma
Other: infects B cells through CD21, atypical lymph on blood smear, + monospot test–heterophile Abs detected by agglutination of sheep or horse RBCs
CMV (HHV-5)
Transmission, Clinical, Other
Transmission: congenital transfusion, sex, saliva, urine, transplant
Clinical: Mononucleosis (– monospot test), infection in immune compromised especially pneumonia in transplants; AIDS retinitis–hemorrhage, cotton-wool exudates, vision loss
Other: Owl Eye inclusions, Latent in mononuclear cells
HHV-6,7
Transmission, Clinical, Other
Transmission: Saliva
Clinical: Roseola infantum (exanthum subitum)–high fevers that can cause seizures followed by macular rash; HHV-7 less common cause
Other:
HHV-8
Transmission, Clinical, Other
Transmission: Sex
Clinical: Kaposi sarcoma (neoplasm of endothelial cells) seen in HIV and transplant patients, presents as dark plaques or nodules representing vascular proliferations
Other: can also affect GI and lungs
Tzanck test
Smeat of an open skin vesicle looking for multinucleated giant cells commonly seen in HSV-1,2 and VZV
Intranuclear inclusion also seen in these viruses
Reoviruses
Naked, dsRNA, linear, icosahedral
Coltivirus: colorado tick fever
Rotavirus: #1 cause of fatal diarrhea in kids
Picornaviruses
Naked, ssRNA, (+) linear, icosahedral All are enteroviruses (fecal-oral) except Rhino (Think PERCH) Poliovirus: polio, Salk/Sabin vaccines Echovirus: aseptic meningitis Rhinovirus: common cold Caxsackievirus: aseptic meningitis, herpangina, hand foot mouth disease, myocarditis, pericarditis Hepatitis A Virus: acute viral hepatitis
Hepevirus
Naked, ssRNA, (+) linear, icosahedral
Hepatitis E virus
Caliciviruses
Naked, ssRNA, (+) linear, icosahedral
Norovirus: gastroenteritis
Flaviviruses
Enveloped, ssRNA, (+) linear icosahedral HCV Yellow Fever Dengue St. Louis Encephalitis West Nile
Togaviruses
Enveloped, ssRNA, (+) linear, icosahedral
Rubella
Western & Eastern Equine Encephalitis
Retroviruses
Enveloped, ssRNA, (+) linear
Have reverse transcriptase
HTLV: T-cell leukemia
HIV: AIDS
Coronaviruses
Enveloped, ssRNA, (+) linear, helical
Common cold, SARS, MERS
Orthomyxoviruses
Enveloped, ssRNA, (-) linear, Helical
Influenza viruses
Paramyxoviruses
Enveloped, ssRNA, (-) linear, Helical
Parainfluenza: croup
RSV: bronchiolitis in babies
Measles, Mumps
Rhabdoviruses
Enveloped, ssRNA, (-) linear, Helical
Rabies
Filoviruses
Enveloped, ssRNA, (-) linear, Helical
Ebola/Marburg hemorrhagic fever–often fatal
Arenaviruses
Enveloped, ssRNA, (+) or (-) circular, helical
LCMV: lymphocytic choriomeningitis virus
Lassa fever encephalitis: spread by rodents
Bunyaviruses
nveloped, ssRNA (-) circular, helical California encephalitis Sandfly/Rift valley fevers Crimean-Congo hemorrhagic fever Hantavirus–hemorrhagic fever, pneumonia
Delta Virus
Enveloped, ssRNA (-) circular, uncertain capsid symmetry
Hepatitis D virus
Yellow Fever Virus
Virus type, Sx
Flavivirus, Aedes Mosquito
Sx: high fever, black vomitus, jaundice, Councilman bodies (eosinophilic apoptotic globules) on liver biopsy
What is the most important global cause of infantile gastroenteritis?
Rotavirus
Rotavirus
Most important global cause of infantile gastroenteritis
Villous destruction and atrophy leads to decreased absorption
What togavirus causes fever, postauricular and other LAD, arthralgias, rash that starts on face and spreads to trunk and extremitites? Causes mild disease in kids but serious congenital disease.
Rubella virus
German Measles or Rubella
Congenital Rubella causes blueberry muffin rash from dermal extramedullary hematopoiesis
Palivizumab
Monoclonal Ab against F protein that is on the surface of Paramyxoviruses and causes epithelial cells to fuse and form multinucleated cells
Viruses include: parainfluenza, mumps, measles, RSV
Describe Croup
Parainfluenza virus (paramyxovirus) Barking cough, inspiratory stridor Narrowing of upper trachea and subglottis leads to steeple sign on x-ray Severe croup can lead to pulsus paradoxus from upper airway obstruction
Describe Rubeola
Measles Virus (paramyxovirus)
3 C’s of measles: Cough, Coryza, Conjunctivitis
Prodromal fever with 3 c’s, then Koplick spots (bright red spots with a blue-white center on buccal mucosa) followed 1-2 days later by maculopapular rash that starts on head/neck and moves down.
Vit A can reduce mobidity and mortality especially in malnourished kids
Describe Mumps
Mumps virus (Paramyxovirus)
Sx: Parotitis, Orchitis, aseptic Meningitis, Pancreatitis
Can cause sterility, especially after puberty
Rabies virus and disease
Bullet shaped virus
Negri bodies: cytoplasmic inclusions commonly in Purkinje cells of cerebellum and in hippocampal neurons
Has long incubation period of weeks to months before Sx onset
Treat with wound cleaning, immunization with killed virus, rabies immunoglobulin
Travels up CNS along neurons by binding Ach receptors
Disease Progression: fever, malaise then agitation, photophobia, hydrophobia, hypersalivation then paralysis, coma then death
Most commonly bat, raccoon, skunk bites in US, can be spread by aerosol in bat caves
Ebola virus and disease
Filovirus
Targets endothelial cells, phagocytes, and hepatocytes
Incubation of 21 days then abrupt onset of flu-like Sx with diarrhea, vomiting, high fever, myalgia
Can progress to DIC, diffuse hemorrhage, and shock
Dx with RT-PCR
Transmission requires contact with bodily fluids or fomites, infected bats or monkeys
No real treatment, must isolate patients
Which hepatitis virus lack an envelope and what does this permit them to do?
HAV and HEV lack envelopes
Not destroyed by gut
Vowels hit your Bowels
How does the DNA polymerase of HBV work?
HBV is the only hepatitis virus that is DNA
The DNA polymerase has DNA and RNA dependent functions
In the nucleus, it first finishes the partial dsDNA of the virus
The host RNA polymerase then makes mRNA from the viral DNA to make viral proteins
Viral DNA polymerase then revers transcribes the viral RNA into DNA for the progeny
Are the hepatitis viruses RNA or DNA?
All RNA except for HBV is DNA
What viral family is each hepatitis virus?
A: picornavirus B: hepadnavirus C: flavivirus D: deltavirus E: hepevirus
How are the hepatitis viruses transmitted?
A: fecal-oral (shellfish, travellers, day care)
B: Blood, Baby making, Birthing (B’s)
C: Blood (IVDU, transfusion)
D: Same as B
E: Fecal-oral, especially waterborne (like A)
Hep viruses incubation times
A: Short B: long C: long D: short (alone), long overall with B E: short
Patient recently returned from Brazil and has sudden onset of fever, retro-orbital pain, headache, joint and muscle pain. Likely Dx?
Dengue Fever
Spread by the Aedes Aegypti mosquito
Sx of Chikungunya
Fever, flu-like, prominent polyarthralgias, diffuse macular rash
Spread by Aedes Aegypti mosquito
What bacteria releases an exfoliative exotoxin leading to scalded skin syndrome? What are the Sx of SSS?
Staph species release this toxin causing Staph Scalded Skin Syndrome (SSSS)
Often happens in infants and young kids
Nikolsky’s sign = sloughing of the skin with gentle pressure, epidermal necrolysis, fever, and pain associated with the rash are common Sx
What is atopy?
A genetic predisposition to develop allergic diseases like allergic rhinitis, asthma, and eczema (atopic dermatitis)
It is a heightened immune response such as a type I hypersensitivity
