Gram Positive Cocci

Question 1

Micrococcus and Staphylococcus

Answer 1

• G+ C in clusters, tetrads, and pairs
• catalase pos.
• facultative anaerobes
• mesophiles (35-37oC)

Question 2

Routine tests

Answer 2

• BA colonial morph.
• gram stain
• catalase
• coagulase
• DNAse (confirmatory)

Question 3

Catalase test (principle)

Answer 3

Determine if an organism produces the catalase enzyme which decomposes hydrogen peroxide (H2O2)

Question 4

All Micrococcaceae and Staphylococcaceae are catalase

Answer 4

Positive

Question 5

Catalase QC organisms

Answer 5

Positive: Staph aureus
Negative: Strep pyogenes

Question 6

Coagulase (principle)

Answer 6

Determine if bacteria produces coagulase to differentiate
Staphylococcus aureus (+) from
Coagulase Negative Staphylococcus

Question 7

Coagulase (how)

Answer 7

clot or clump plasma due to formation of fibrin from fibrinogen

Question 8

Two types of coagulase

Answer 8

• bound (clumping factor, on cell wall)

- free (excreted)

Question 9

Coagulase QC organism

Answer 9

Positive: staph aureus
Negative: staph epidermidis

Question 10

Slide coagulase

Answer 10

• bound coagulase

- clumping factor reacts directly with fibrinogen → agglutination

Question 11

Tube coagulase

Answer 11

• free coagulase
• forms a complex with CRF and this reacts with fibrinogen → clot
  (Do when slide coag. neg.)