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
Why are ahminoglycosides ineffective against anaerobes?
ahminoglycosides require O2 to enter into bacterial cells.
obligate intracellular bugs
why are certain bugs obligate intracellular?
rely on host ATP production
facultative intracellular bugs?
immunologic response to encapsulated bacteria?
Opsonized, then cleared by spleen.
what vaccines do asplenics need?
1) s pneumo
2) h flu
3) n menigitidis
why are vaccines conjugated to a carrier protein?
promotes T-cell activation and class switching
what is the pneumococcal vaccine?
1) Pneumococcal conjugate vaccine (PCV), ie Prevnar
2) PPSV, pneumococcal polysaccharide vaccine with no conjugated protein, i.e. Pneumovax
Other conjugate vaccines?
- H influenza type B
- meningococcal vaccine
hydrolyzes urea to release ammonia + CO2, thus increasing pH.
Degrades H2O2 into H2O and bubbles of O2. This prevents H2O2 from being converted to microbicidal products by myeloperoxidase.
Catalase positive organisms?
s aureus pigment?
yellow (aureus is latin for gold)
Other biofilm-producing bug?
*Nontypeable H influenza
What does nontypeable mean?
Contact-lens associated keratitis caused by?
s aureus virulence factor?
protein A; prevents opsonization and phagocytosis
bugs that have an IgA protease?
1) S pneumonia
2) H flu type B
Function of M protein?