Micro Flashcards
MacConkey agar inhibits which bacterial species? In what way is it a differential medium?
Inhibits G+ through use of bile salts and crystal violet dye (lack thick wall of G-), selective for G- (but NOT fastidious G-)
Differential b/c allows for the differentiation of G- based on lactose fermentation. The better they ferment, the more red the colonies look; less fermentation is pink. Non fermenters are colorless.
EMB agar (eosin methylene blue agar) is both selective and differential is what way? What color would E.coli look like on this plate, Klebsiella pneumonia, proteus mirabilis ?
Selects for G- much like MacConkey agar by using a dye (methylene blue). G+ and fastidious G- can not grow on it.
Its differential also based on lactose fermentation, but the color changes are based on pH changes. Acidic is black to dark purple or brown, due to lactose fermentation, non fermenters look pink or translucent. E.coli has a metallic green sheen, Klebsiells would look dark purple or brown, proteus pink.
The urease test is what type of test? Is it selective or differential? What does a positive and negative result look like?
Tests the ability of a microbe to breakdown urea into ammonia and CO2. When the pH rises as a result the indicator in a tube turns from a yellow to a fusha pink. This is a differential test (+ or -). Test can also be done using agar slants.
Some of the enterobacteriaceae bacteria like Proteus mirabilis, Klebsiella pneumoniae, Serratia marcescens, are ureas +
What type of test is mannitol salt agar? Is it selective or differential?
It’s both selective and differential. It’s used to differentiate G+/G- (G+ grow on salt), and then select based on G+ ability to ferment mannitol.
How do all fungi gram stain?
Gram +
Urinalysis results indicate pH of 8, nitrates, and leukocyte esterase whats the most likely organism?
Proteus mirabilis
UA results indicate a nitrate negative, leukocyte positive organism that’s non hemolyitic in a young sexually active woman. What;s the most likely etitology?
Staph. Saprophyticus
When do you need to culture with suspected UTI?
When the symptoms are not consistent with the dipstick reading, recurrent UTI, or patient has signs of upper respiratory tract infection.
How can you get a steril pyuria?
Post antibiotic
Frequent recurrent UTI’s are defined how?
2 in 6 months, or 3 in 1 yr
Name 3 catagories of helminths (parasitic worms) and identify which category schistosomes belong in.
cestodes=tapeworms
nematodes=round worm (nice and round)
Trematodes=fukes
Schistosomes are Trematodes.
What is the definitive and intermediate host of a schistosome?
Definitive host is human adults (where sexual reproduction occurs); infected by cercariae in contaminated water.
Intermediate host freshwater snail (asexual reproduction to produce cercariae)
How many intermediate hosts due schistosomes have? What are three problems that they cause in humans?
1 intermediate host - freshwater snail
Problems- obstruction of organs (like ureter), develop a secondary bacterial infection, squamous cell carcinoma.
You have a patient who recently immigrated from the middle east in your clinic who’s urine was positive for parasitic eggs with a terminal spine. How might the adult parasites in this host increase in number?
Only via additional exposure, because the eggs are shed
This is schistosoma
How do people with schistosoma get bladder cancer?
From eggs which are carcinogens
