Which statement correctly describes the Nagler reaction used in the identification of Clostridium perfringens?

• A It detects the presence of enterotoxin using reverse passive latex agglutination
• B It identifies the organism by its ability to ferment lactose and produce acid on MacConkey agar
• C It demonstrates double zone of hemolysis on blood agar with complete hemolysis in the inner zone
• D It detects lecithinase activity on egg yolk agar, producing an opacity zone that is inhibited by specific antitoxin ✓

Explanation

The Nagler reaction demonstrates lecithinase (phospholipase/alpha toxin) activity of C. perfringens on egg yolk agar. One half of the plate contains antitoxin; opacity develops only on the antitoxin-free half, confirming the reaction is specifically neutralized by anti-alpha toxin. The double zone of hemolysis is a separate identification feature on blood agar but not the Nagler reaction itself. Enterotoxin detection is a separate assay.

Reference: Jawetz, Melnick, and Adelberg's Medical Microbiology, 28th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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