A Gram-stained smear from a pus swab shows Gram-positive cocci in clusters. Which single rapid laboratory test best distinguishes this isolate from Streptococcus species?
- A Bacitracin sensitivity test
- B Coagulase test
- C Catalase test ✓
- D Optochin disc test
Correct answer: C. Catalase test
Explanation
Staphylococci produce catalase and convert hydrogen peroxide to water and oxygen with effervescence, whereas streptococci are catalase negative because they lack the enzyme. This single test separates the two genera at the first step of identification. Coagulase comes later and only separates S aureus from other staphylococci, so it cannot distinguish staphylococci from streptococci.
Reference: Jawetz, Melnick and Adelberg's Medical Microbiology, 28th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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