Clinical Bacteriology Flashcards
How would you culture for lactose-fermenting bacteria?
MacConkey’s agar - turns pink with lactose fermenters such as E. coli. E. coli is also grown on eosine-methylene blue agar ->blue-black colonies w/ metallic sheen.
What 3 vaccinations would you make sure to give before a splenectomy? Why?
N. meningitidis, S. pneumonia, and H. influenzae b/c asplenic individuals have a decreased ability to opsonize encapsulated pathogens.
Name 3 organisms that might cause recurrent infections in a person with chronic granulomatous disease. Why does this happen?
Catalase (+) organisms: SSPACE
S. aureus, Serratia, Pseudomonas, Actinomyces/Aspergillus, Candida, E. coli.
CGD is due to NADPH oxidase deficiency, which produces reactive oxygen species -> H2O2 ->hypochlorite for the oxidative burst. Catalase destroys the little H2O2 that might be available for this process.
Which bugs are urease (+)?
PUNCH-K Proteus Ureaplasma Nocardia Cryptococcus H. pylori Klebsiella
How does Protein A increase the virulence of S. aureus?
It binds the Fc portion of Ig, preventing opsonization and phagocytosis.
Which bacteria have IgA protease?
SHiN
S. pneumonia
Haemophilus influenzae
Neisseria
What virulence factor prevents phagocytosis of GAS?
M protein
What superantigen is produced by S. aureus? Strep. pyogenes?
TSST-1, Exotoxin A
How do the exotoxins of Corynebacterium diphtheriae and Pseudomonas work?
inactivate elongation factor 2 (EF-2). (diphtheria toxin and Exotoxin A)
Mechanism of Shiga toxin
inactivates 60S ribosome by cleaving rRNA
What bacteria produces Shiga-like toxin? How is this bacterium different from Shigella?
EHEC. Does not invade cells.
What syndrome outside of the GI tract are Shigella and EHEC known to cause? Which strain of EHEC does this?
HUS
E. coli O157:H7
