Micro lab quiz 5
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What is a carbohydrate fermentation media? What information does it provide?
- Broth media with phenol red
- if sugar is fermented, acid forms, Phenol red changes color
what is phenol red and why is it used in fermentation tests?
- pH indicator
- turns yellow when pH is lowered -> indicates fermentation
What is a Durham tube? What information does it provide?
indication of gas production
What is superoxide dismutase?
catalyzes conversion of superoxide radicals (O2-) to hydrogen peroxide
what is the catalase test/what does catalase do? What information does it provide/what indicates a positive result?
Catalase breaks down hydrogen peroxide (H2O2) to water and gaseous oxygen
- Positive result: bubbles -> presence of catalase
- positive: microcaccae
- negative: streptocaccae
What is the nitrate reduction test? What information does it provide?
Differentiates Enterobacteriaceae from Gram negative rods that don't reduce nitrate or reduce it past nitrite
Tells us if the organism reduces nitrate to nitrite
What type of media is Phenylethyl Alcohol Agar (PEA) test?
What does it test for?
Isolates what two organisms?
- undefined, selective
- encourages Gram positive organisms
- Phenylethyl Alcohol inhibits Gram negative organisms by breaking down their membrane
- Isolates stapylococci and streptococci
What type of media is Mannitol Salts Agar (MSA) Test and what info does it provide?
- differential and selective
- Selects for staphylococcus aureus
- -bright yellow colonies with yellow halo
What type of media is the MacConkey Agar (Mac) Test? What info does it provide? positive result?
differentiates between members of _____
- selective and differential
- isolate and differentiate between different members of Enterobacteriacae
- based on ability to ferment lactose
- positive: turns pink -> can ferment lactose
Eosin methylene Blue (EMB) Agar test
isolates what organism/organisms that do what?
- complex, selective, differential
- inhibits Gram positive
- isolate fecal coliforms
- lactose fermenters change color
- E. coli = dark purple/black with green sheen
Hektoen Enteric Agar (Hek) Test
isolates what two organisms
complex, moderately selective, differential
Isolate salmonella (black) and shigella (blue-green)
Xylose Lysine Desoxycholate (XLD) Test
Isolates what two organisms
Shigella and Providencia
decarboxylate lysine -> red
Blood Agar Test for Hemolysis isolates/cultivates _________
detects presence of _______________
- fastidious bacteria
Enterotube is good for __________ identification of enterobacteriaceae
What would you like to do?
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