Micro Lab POM Flashcards
A catalase test distinguishes between what bacteria?
Staphylococci (catalase positive) and streptococci (catalase negative)
What is catalase?
Catalase is an enzyme that catalyzes the breakdown of hydrogen peroxide into water and oxygen.
What is coagulase?
Coagulase is bacterial enzyme that allows the conversion of fibrinogen to fibrin
A coagulase test distinguishes between what bacteria?
S. aureus (coagulase positive) and S. epidermidis (coagulase negative)
Why does S. aureus have a positive coagulase test?
When S. aureus comes into contact with blood, it coats its surface with a fibrin barrier, which protects the bacteria from phagocytosis and antimicrobial agents
What does an oxidase test identify?
Identifies bacteria that produce the enzyme cytochrome oxidase, aka they can use oxygen as an electron acceptor to generate energy
An oxidase test can distinguish between what bacteria?
Can distinguish the follow bacteria (all of which are oxidase positive): Neisseria spp., Pseudomonas spp., and M. catarrhalis.
Explain how sheep blood agar plates can differentiate bacteria:
Some bacteria produce exotoxins called hemolysins. The bacteria can be distinguished by their ability to lyse RBCs (gamma is no RBC destruction, alpha is partial, and beta is complete destruction)
A P-disc test can distinguish between what bacteria?
Can distinguish S. pneumoniae (optochin sensitive) from other alpha-hemolytic streptococci spp. (optochin resistant)
What does a P disc test for?
P disc is used to determine optochin sensitivity.
an A disc can distinguish between what bacteria?
Can distinguish group A streptococci (e.g. S. pyogenes) from other B-hemolytic Streptococci (e.g. Non Group A B-hemolytic Streptococci)
What does an A disc test for?
Bacitracin sensitivity
What can a Bile Esculin test identify?
Positive bacteria hydrolyze esculin to produce a product that interacts with iron in the media to yield black complex
A bile esculin test can distinguish between what bacteria?
Can distinguish Enterococcus faecalis from other gamma-hemolytic bacteria
