Question

Which of the following test is used to differentiate Staphylococcus aureus from other Staphylococcus species?

• A. Catalase Test
• B. Oxidase Test
• C. Coagulase Test
• D. Urease Test

Hint:

Remember: Coagulase-positive = Staphylococcus aureus. Other staphylococci are coagulase-negative.

Answer 1

The Correct Option is C

Step 1: Role of laboratory tests.
Microbiological identification of bacteria often depends on biochemical tests. Among the staphylococci, different tests help to distinguish one species from another.
Step 2: Understand Staphylococcus aureus.
Staphylococcus aureus is the most pathogenic species of the staphylococci. It is coagulase-positive, meaning it can clot plasma by producing the enzyme coagulase. This test is therefore a reliable method to identify it.
Step 3: Analyze each option.
- (A) Catalase Test: This test differentiates staphylococci (catalase-positive) from streptococci (catalase-negative). It cannot distinguish between different staphylococcus species.
- (B) Oxidase Test: Used to identify organisms like Pseudomonas, not useful for staphylococci.
- (C) Coagulase Test: Correct. Staphylococcus aureus is coagulase-positive, while most other staphylococcal species are coagulase-negative. This is the gold standard test.
- (D) Urease Test: Not specific for staphylococci; mainly used in differentiating Proteus, Klebsiella, and Helicobacter.
Step 4: Conclusion.
The coagulase test is the most reliable way to differentiate Staphylococcus aureus from other staphylococcal species.