Bacteria Flashcards
All bacterial capsules contain polysaccharide except which one?
Bacillus anthracis which contains D-glutamate (a polypeptide)
Are lipoteichoic acids on gram positives or negatives?
Positives
What do lipoteichoic acids induce in host’s immune system?
TNF and IL-1
What does Lipid A induce in host’s immune system?
TNF, IL-1, and IL-6
Is endotoxin (LPS) on gram positives or negatives?
Negatives
Where exactly are beta-lactamases located on a bacterium?
In the periplasm layer of gram negatives
What is the purpose of a bacterium’s capsule?
Protects against phagocytosis
What does catalase do?
Catalyzes the following reaction: 2H2O2 –> O2+2H2O
What is LPS composed of?
Lipid A (toxic), core polysaccharides, and O antigen
A deficiency in C5-C9 predisposes a patient to disease by which species of bacteria?
Neisseria
What are the 7 Gram positive rod species?
Clostridium, Propionibacterium acnes, Gardnerella, Corynebacterium, Bacillus, Listeria, Mycobacterium
What are the 2 pleomorphic bacterial species? And which stain must you use to visualize them?
Rickettsiae and Chlamydiae; Giemsa stain
What are the 3 spirochete bacterial species? And how can you visualize them?
Borrelia, Leptospira, Treponema; Dark field microscopy
Which bacterial species has no cell wall?
Mycoplasma
Giemsa stain is used to visualize which bacterial species?
Chlamydia, Borrelia, Rickettsiae, Trypanosomes, Plasmodium; “Certain Bugs Really TRY my Patience”
PAS stain is used to visualize which bacterial species?
Stains glycogen, used to diagnose Whipple disease (Tropheryma whipplei)
Ziehl-Neelsen (carbol fuchsin) stain is used to visualize which bacterial species?
Acid-fast organisms (Nocardia, Mycobacterium)
India ink stain is used to visualize what?
Cryptococcus neoformans
Silver stain is used to visualize what?
Fungi, Legionella, H pylori
Chocolate agar with factors V (NAD+) and X (hematin) is used to grow which bug?
H flu
Thayer-Martin agar (or VPN) media contains what?
Vancomycin (inhibits gram +), Polymyxin (inhibits gram - except Neisseria), and Nystatin (inhibits fungi)
Thayer-Martin agar (or VPN) is used to isolate which bug?
Neisseria spp.
Bordet-Gengou (potato) agar is used to isolate which bug?
Bordetella pertussis
Tellurite agar (Loffler medium) is used to isolate which bug?
C diphtheriae
Lowenstein-Jensen agar is used to isolate which bug?
Mycobacterium TB
Eaton agar - which bug?
M pneumoniae “don’t EAT ON ice”
Charcoal yeast extract agar buffered with cysteine and iron (aka BYCE) is used to isolate which bug?
Legionella “SS Cysteine”
Sabouraud agar is used to isolate what?
Fungi
Which bugs are obligate aerobes?
Nocardia, Pseudomonas, and MycoBacterium “Nagging Pests Must Breathe”
Which bugs are obligate anaerobes?
Clostridium, Bacteroides, and Actinomyces (lack catalase and/or superoxide dismutase) “anaerobes Can’t Breathe Air”
Which class of antibiotic is ineffective against anaerobes?
Aminoglycosides
Which bugs are obligate intracellular?
Rickettsia, Chlamydia
Which bugs are facultative intracellular?
Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella, Yersinia pestis; “Some Nasty Bugs May Live FacultativeLY”
Which bacteria are encapsulated?
S pneumo, H flu, Neisseria meningitidis, E coli, Salmonella, Klebsiella pneumo, group b Strep ; “SHiNE SKiS”
Patients with chronic granulomatous disease are susceptible to which organisms?
Catalase positive organisms because they are deficient in NADPH oxidase
How does Protein A evade the immune system and which bug is it associated with?
S aureus; Binds Fc region of IgG and prevents opsonization and phagocytosis
Which bugs express IgA protease?
S pneumo, H flu type B, and Neisseria
How does M protein evade the immune system and which bug is it associated with?
Group A strep; Helps prevent phagocytosis
Which 5 bugs are lactose fermenters?
E coli, Klebsiella, Enterobacter, Citrobacter, Arizona
What is the heat stability of endotoxin?
Stable at 100 degrees C for 1 hour
What is the genetic location of genes of exotoxins? Of endotoxins?
Plasmid/bacteriophage and bacterial chromosome, respectively
What is the heat stability of exotoxin?
Destroyed rapidly at 60 degrees C (except staph enterotoxin)
What are the names and mechanisms of Staph aureus’ exotoxins?
TSST-1; Brings MHC II and TCR in proximity to outside of antigen binding site to cause overwhelming release of IFN-gamma and IL-2 –> shock
Enterotoxin; Rapid-onset food poisoning
Exfoliative toxin; Scalded skin syndrome
What are the names and mechanisms of E coli’s exotoxins (3)?
Shiga-like toxin (SLT) EHEC; Inactivates 60S ribosome by removing adenine from rRNA –> dysentery
Heat-labile toxin (LT) ETEC; Overactivates AC to increase cAMP which leads to increased Cl secretion in gut and water efflux
Heat-stabile toxin (ST) ETEC; Overactivates GC to increase cGMP which leads to decreased resorption of NaCL and water in gut
What is the name and mechanism of Vibrio cholerae’s exotoxin?
Cholera toxin; A-B toxin that overactives AT and increases cAMP by permanently activating Gs –> increased Cl secretion in gut and water efflux –> “rice water” diarrhea
What are the names and mechanisms of Streptococcus pyogene’s exotoxins?
Streptolysin O; Protein that degrades cell membrane
Exotoxin A; Brings MHC II and TCR in proximity to outside of antigen binding site to cause overwhelming release of IFN-gamma and IL-2 –> shock
What is the name and mechanism of Bacillus anthracis’ exotoxin?
Edema factor; Mimics the AC enzyme to increase cAMP
What is the name and mechanism of Bordetella pertussis’ exotoxin?
Pertussis toxin; Overactivates AC (increasing cAMP) by ribosylating and disabling Gi, impairing phagocytosis to permit survival of microbe
What is the name and mechanism of Clostridium perfringens’ exotoxin?
Alpha toxin; Phospholipase (lecithinase) that degrades tissue and cell membranes
What is the name and mechanism of Shigella’s exotoxin?
Shiga toxin; Inactivates 60S ribosome by removing adenine from rRNA, ST also enhances cytokine release causing HUS
What is the name and mechanism of Pseudomonas aeruginosa’s exotoxin?
Exotoxin A; Inactivate EF-2
What is the name and mechanism of Clostridium botulinum’s exotoxin?
Botulinum toxin; Cleaves Snare proteins that release ACh vesicles –> descending flaccid paralysis
What is the name and mechanism of Clostridium tetani’s exotoxin?
Tetanospasmin; Cleaves Snare proteins that release GABA and glycine vesicles –> spastic paralysis
What is the name and mechanism of Corynebacterium diphtheriae’s exotoxin?
Diphtheria toxin; ADP-ribosylationof EF-2 prevents protein synthesis
What is the most common cause of septic arthritis?
S aureus
What is the most common cause of osteomyelitis?
S aureus
What is the treatment for MRSA?
Vancomycin
What is the treatment of MSSA?
Naphcillin
What is the treatment for staph epidermidis and saprophyticus?
Vancomycin
What is the second most common cause of UTIs in sexually-active young women?
Staph saprophyticus
Strep pneumo is the #1 cause of what?
“MOPS” Meningitis, otitis media (kids), pneumonia, and sinusitis
Pneumonia with rust-colored sputum may indicate infection with what bug?
S pneumo
What is the virulence factor of S pneumo?
IgA protease, capsule
What is the treatment of S pneumo?
Macrolides or ceftriaxone
The adult S pneumo vaccine is what kind of vaccine?
A polysaccharide vaccine with an IgM response
The child S pneumo vaccine is what kind of vaccine?
A conjugate vaccine with an IgG response
What is the #1 cause of necrotizing fasciitis?
Group A strep (S pyogenes) - specifically SPEb protease toxin
S pyogenes capsule is made of what?
Hyaluronic acid (also found in humans, therefore not immunogenic)
What is the #1 cause of erysipelas?
S pyogenes
What causes Scarlet fever?
SPE exotoxin of S pyogenes
What are the main symptoms of scarlet fever?
Reddening of the tongue, pharyngitis, widespread rash that spares the face
Which bug causes Toxic shock-like syndrome?
S pyogenes
How long after infection does post-strep glomerulonephritis occur?
2 weeks after onset of initial infection
What is the main virulence factor responsible for rheumatic fever?
M protein of S pyogenes - prevents phagocytosis
In bacterial genetics, what is Transformation?
Ability to take up DNA (from cell lysis) from environment.
In bacterial genetics, what is Conjugation?
Two types of conjugation
F+ x F- : F+ plasmid contains genes for sex pilus and conjugation. Plasmid (dsDNA) is replicated and transferred through pilus from F+ cell to F- cell. No transfer of chromosomal genes.
Hfr x F- : F+ plasmid can be incorporated into bacterial chromosomal DNA (high frequency recombination). Replication of incorporated plasmid DNA may include some flanking chromosomal DNA.
In bacterial genetics, what is Transposition?
Segment of DNA (transposon) that can “jump” from one location to another, can transfer genes from plasmid to chromosome and vice versa. Excision may include some flanking chromosomal DNA, which can be incorporated into a plasmid and transferred to another bacterium.
In bacterial genetics, what is Generalized Transduction?
Lytic phage infects bacterium, leading to cleavage of bacterial DNA. Parts of bacterial chromosomal DNA may become packaged in viral capsid. Phage infects another bacterium, transferring these genes.
In bacterial genetics, what is Specialized Transduction?
Aka prophages. 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 viral capsid and infects another bacterium.
Genes for which 5 bacterial toxins are encoded in lysogenic phages?
Shiga-like toxin, Botulinum toxin, Cholera toxin, Diphtheria toxin, Erythrogenic toxin of S pyogenes
Which virulence factor of S pyogenes is responsible for rheumatic fever and why?
M protein - Very antigenic and illicits a very strong humoral response. Molecular mimicry causes Abs to attack the myosin in cardiac muscle.
What is the most severe form of rheumatic fever?
Myocarditis
What is the clinical presentation of rheumatic fever?
Acute migratory polyarthritis, carditis, subcutaneous nodules, erythema marginatum, Sydenham chorea (JONES criteria)
How does acute glomerulonephritis from a GAS infection present?
Cola-colored urine and facial edema
How can we detect a recent GAS infection?
ASO titer (anti-streptolysin O antibodies)
Can early treatment of GAS infection prevent rheumatic fever?
Yes
Can early treatment of GAS infection prevent acute glomerulonephritis?
No
What is the treatment of GAS infection?
Penicillin
What is the role of GAS’s virulence factor streptokinase?
Converts plasminogen –> plasmin *plasmin is fibrinolytic
What is the role of GAS’s virulence factor streptolysin O?
(Oxygen labile) Lyses RBCs
What does GBS cause in babies?
Pneumonia, meningitis, and sepsis.
Which Strep bacterium tests hippurate positive?
GBS
What is the CAMP test and what does it test for?
GBS; GBS produces CAMP factor, which enlarges the area of hemolysis of S aureus
Which of the two enterococi is more common?
Enterococcus faecalis > Enterococcus faecium
What is a common bug that causes subacute endocarditis following GI/GU procedures?
Enterococcus
What are the three most common diseases caused by enterococcus?
UTIs, biliary tract infections, and subacute endocarditis
What can be used to treat enterococcus?
Linezolid or tigecycline (resistant even to vancomycin, VRE)
What is the most life-threatening manifestation of Corynebacterium diphtheriae?
Myocarditis and arrhythmias
What test is used to determine the toxicity of Corynebacterium diphtheriae?
Elek test for toxin
What kind of vaccine is the vaccine for Corynebacterium diphtheriae?
Toxoid - IgG response
A blood infection with Strep bovis would cause you to look for what in a patient?
Colon cancer
What kind of vaccine is the tetanus vaccine?
Toxoid
Describe floppy baby syndrome
Ingestion of spores of Clostridium botulinum causes flaccid paralysis - adults cannot get sick with spores due to mature gut flora
Is C botulinum an ascending or descending paralysis?
Descending
What are the 2 diseases caused by C perfringens?
Gas gangrene and late-onset food poisoning (ingestion of spores)
What is the treatment of C perfringens?
IV penicillin G
Which clostridium species causes a double zone of hemolysis on blood agar?
C perfringens
What toxins are produced by C dif and what are their mechanisms of action?
Exotoxin A: Binds to brush border and causes inflammation, cell necrosis, and watery diarrhea
Exotoxin B: Disrupts cytoskeleton integrity by depolymerizing actin –> pseudomembranous colitis
How is C diff diagnosed?
Detection of one or both toxins in the stool
How is C diff treated?
Metronidazole or oral vancomycin. Recurring cases may benefit from fecal transplant.
What are anthrax’s toxins and their MOAs?
EF (edema factor): Activates AC, increase in cAMP, edema, indirectly prevents phagocytosis
LF (lethal factor): Exotoxin that acts as a protease and cleaves map kinase –> tissue necrosis
What is the treatment of Bacillus anthracis?
Fluoroquinolones or doxycycline