Virtual Lab 3
Staphylococci
Gram Stain
- organism: Staphylococcus aureus
- reaction: gram positive
- morphology/arrangement: staphylo/cocci…clusters, round bacteria
Catalase Test
- Staphylococci are typically strongly positive for the reaction
Mannitol Salt Agar Plate (MSA)
- selective component: high salt
- differential component: mannitol
| Sector | Growth? | Fermentation of mannitol? | Interpretation |
|---|---|---|---|
| A | +++ | Yes (reduction of phenol red - yellow) | Presumptive ID of Staphylococcus aureus |
| B | +++ | No | Staphylococcus species (but not S. aureus) |
| C | --- | No | Not a Staphylococcus species |
Coagulase Test
- detects the presence of coagulase enzyme that can coagulate plasma
- is a definitive test for Staphylococcus aureus
Streptococci
Representative Streptococcus
- Gram stain reaction: Gram positive
- Morphology, arrangement: coccus-shaped organism in chains
Blood Agar Plate
Organism: Streptococcus pyogenes
- Hemolysis type: Beta ()
- Optochin (P disc) sensitivity: Resistant
- Bacitracin (A disc) sensitivity: Sensitive
Representative Streptococcus
