Which test is most appropriate for presumptive identification of Clostridium perfringens?

• A. SPS sensitivity test
• B. Reverse CAMP test
• C. Cytotoxin assay
• D. Esculin hydrolysis

Answer: (B)

Presumptive identification of Clostridium perfringens hinges on its interaction with a CAMP-factor–producing organism on blood agar. In the reverse CAMP test, Staphylococcus aureus is streaked in a line on blood agar and the test organism is placed at right angles. Clostridium perfringens produces an alpha-toxin (lecithinase) that interacts with the CAMP factor from S. aureus to create a distinct, enhanced hemolysis pattern in the area opposite the S. aureus line. This characteristic appearance makes the reverse CAMP test the best choice for presumptive identification of C. perfringens.

The other tests aren’t as diagnostic for this organism: SPS sensitivity is not specific for C. perfringens, esculin hydrolysis is used to differentiate enterococci and related groups, and cytotoxin assays are more relevant to other pathogens (like detecting toxins from C. difficile) rather than serving as a quick presumptive ID for C. perfringens.