TESTS FOR IDENTIFICATION OF STAPHYLOCOCCI (Biochemical methods of identification)

Question 1

A biochemical test for differentiating Staphylococcus and Streptococcus

Answer 1

Catalase test

Question 2

Catalase test characteristics

positive result: ________
negative result:________

Answer 2

Catalase test:

positive: rapid continuous bubbles/effervescence
negative: lack of bubble formation 30 seconds later

Question 3

Enumerate the Catalase-Positive organisms:

Answer 3

• Nocardia
• Pseudomonas
• Listeria
• Aspergillus
• Candida
• E. coli
• Staphylococcus
• Serratia
• Burkholderia cepacia
• H. pylori

mnemonic: “CATs Need PLACESS to Belch their Hairballs”

Question 4

Coagulase is a test for:

Answer 4

S. aureus vs other Staphylococcus (S. epidermidis, S. saprophyticus)

S. aureus - catalase (+)

Question 5

Coagulase slide test detects:
Coagulase tube test detects:

Answer 5

Slide test: detects bound coagulase (clumping factor)
Tube test: detects free coagulase

Question 6

Positive coagulase test appearance:

Answer 6

Positive: white fibrin clots in plasma

Question 7

A test for S. saprophyticus vs other CoNS (Coagulase Negative Staphylococcus)

Answer 7

Novobiocin Susceptibility Test

Question 8

In the novobiocin susceptibility test, S. saprophyticus is:

Answer 8

Novobiocin Susceptibility Test:

S. saprophyticus: Resistant
S. epidermidis: Susceptible

Mnemonic: No StRES
No - Novobiocin
S - saprophyticus is
t
R - Resistant
E - epidermidis is
S- Susceptible

Question 9

Susceptible zone diameter in novobiocin:
Resistant zone diameter in novobiocin:

Answer 9

Susceptible: >16 mm
Resistant: <16

Question 10

DNase positive organisms:

Answer 10

S. aureus
Moraxella catarrhalis
Serratia marcescens

mnemonic: SMS

Question 11

Positive result in DNase test:

Answer 11

Hydrolysis of the surrounding medium, resulting in a clear zone

Question 12

Selective and differential for Staphylococcus species:

Answer 12

Mannitol Salt Agar

Question 13

A Staphylococcus spp that can ferment mannitol and turns phenol-red into yellow in MSA:

Answer 13

MSA (Mannitol Salt Agar)

Staphylococcus aureus: red—>yellow
Other Staph: red