Microbiology - Staphylococci and Streptococci Review

Flashcards covering key microbiological concepts related to Staphylococci and Streptococci, including characteristics, tests, and specific organisms.

Staphylococcus aureus

Gram positive cocci in clusters, catalase positive, and coagulase positive; typically exhibits beta hemolysis on blood agar.

Staphylococcus epidermidis

Gram positive cocci in clusters, catalase positive, coagulase negative; exhibits gamma hemolysis on blood agar.

Catalase Test

A test used to identify organisms that produce the enzyme catalase, resulting in the conversion of hydrogen peroxide to water and oxygen.

Mannitol Salt Agar

A selective medium used to differentiate Staphylococcus aureus (ferments mannitol, turning the agar yellow) from Staphylococcus epidermidis (does not ferment mannitol, remains pink).

Enterococcus faecalis

Only Streptococcus that grows in 6.5% NaCl; classified in Lancefield Group D and exhibits gamma hemolysis.

Streptococcus pyogenes

Lancefield Group A, beta hemolytic, susceptible to bacitracin, negative for beta-lactamase.

Streptococcus pneumoniae

Not classified in a Lancefield group, alpha hemolytic with mucoid appearance due to capsule, and susceptible to optochin.

Escherichia coli

A lactose fermenter that produces dark pink/red colonies on MacConkey agar, positive for indole and motility.

Proteus mirabilis

A non-lactose fermenter that shows clear colonies on MacConkey agar, positive for motility and H2S production.

Pseudomonas aeruginosa

A non-lactose fermenter that may produce green pigment and is positive for oxidase test; shows clear, football-shaped colonies.

Bile Esculin Test

Used to identify Enterococcus and Streptococcus species by determining their ability to hydrolyze esculin in the presence of bile.