Flashcards in ID 2 Deck (51)
Why can't you stain mycobacteria?
cell wall has high lipid content
why can't you stain mycoplasma/ureaplasma?
no cell wall
Why can't you stain chlamydia?
primarily intracellular + lacks classic peptidoglycan because of decreased muramic acid.
What other bugs can't you stain and why?
Intracellular like Legionella, rickettsia, chlamydia, bartonella, ehrlichia, anaplasma
Giemsa staining for
What does PAS stain?
other name for Ziehl-Neelsen
What else can you use Ziehl-Neelsen for
1) acid-fast bacteria (nocardia)
2) protozoa (cryptosporidum oocysts)
Alternative stain for acid-fast bacteria to Ziehl-Neelsen and characteristics of test?
Auramine-rhodamine for screening (cheep, more sensitive but less specific)
stains thick polysaccharide capsule of cryptococcus red
what else do you use silver stain for?
3) H pylori
What can you stain viruses with?
Fluorescent antibody stain
Example of selective media
Thayer-Martin (contains antibiotics)
significance of differential/indicator media?
yields a color change in response to metabolism of certain organisms
example of indicator differential media?
MacConkey (contains a pH indicator)
culture requirements for H influenza?
Factors V (NAD+) and X (hematin)
n meningitides media?
How does Thayer-Martin agar work?
1) inhibits gram positives with vancomycin
2) inhibits gram negatives (except neisseria obviously) with trimethoprim and colistin
3) inhibits fungi with nystatin
what does Regan-Lowe medium contain?
Charcoal, blood, antibiotic
M pneumonia media?
Eaton agar. Requires cholesterol.
Effect on MacConkey agar?
Used for lactose-fermenting enterics. Fermentation produces acid, causing colonies to turn pink.
e coli medium?
eosin-methylene blue (EMB) agar
affect of EMB agar
colonies with green metallic sheen
charcoal yeast extract buffered with cysteine and iron
What do you stain fungi with?
1) susceptible to oxidative-damage (don't have catalase or superoxide dismutase)
2) foul smelling (short-chain fatty acids)
3) hard to culture
4) produce gas in tissue (CO2 and H2)
5) normal flora in GI tract but pathogenic elsewhere