Tests for Micrococcus and Staphyloc Flashcards
Test for Micrococcus and Staphylococcus
Catalase Test
Screening test for Gram-positive organisms, differentiates Micrococcaceae from Streptococci
Catalase Test
Chemical reaction in Catalase Test
O2 + H2O2 → H2O and O2
Reagent for Catalase Test
3% or 30% hydrogen peroxide, 22-25°C
Positive QC for Catalase test: Copious bubbles/effervescence (positive)
S. aureus; False pos loop contaminated with blood agar
Negative QC for Catalase test No or weak effervescence (negative)
Streptococci (e.g., S. pyogenes)
Differentiate Micrococci from Staphylococci
Microdase (Modified Oxidase) test
Chemical reaction in Microdase test
Oxidase + reagent + Cytochrome C → Indophenol blue
Incubation conditions for Microdase test
22-25°C, 2 minutes
Positive QC for Microdase test: Blue to Purple-blue (positive)
Micrococcus luteus
Negative QC for Microdase test: No color change (negative)
S. aureus
Differentiate S. aureus from CoNS
Coagulase test
Chemical reaction in Coagulase test
Coagulase activates coagulase-reacting factor (CRF), a modified thrombin, which activates fibrinogen to fibrin clot
Reagent for Slide method coagulase test
Drop of EDTA Rabbit plasma
Incubation conditions for Slide method coagulase test
22-25°C, 5-10 seconds
Positive QC for Slide method: Clumping (positive)
S. aureus in rabbit plasma
Negative QC for Slide method: No clumps (negative)
S. epidermidis in water/saline
Reagent for Tube method coagulase test
0.5 mL EDTA Rabbit plasma
Incubation conditions for Tube method coagulase test
35-37°C, 1-4 hours
Positive QC for Coagulase Tube method: Clot (positive)
S. aureus in rabbit plasma
Negative QC for Coagulase Tube method: No clot (negative)
S. epidermidis in water/saline
Distinguish S. aureus, Serratia, and M. catarrhalis
DNase test
Chemical reaction in DNase test
DNA/Methyl Green complex + deoxyribonuclease → colorless
Media for DNase test
DNase agar
Reagent for DNase test
Methyl green
Incubation conditions for DNase test
35-37°C, 13-24 hours