Reverse CAMP test for the identification of Clostridium perfringens
Hansen used the synergistic relationship between the two microbes to develop a test, known as the reverse CAMP test, using Streptococcus agalactiae for the identification of Clostridium perfringens. Alpha toxin producing C. perfringens and group B, β-haemolytic streptococci grow in a characteristic pattern on blood agar.
The test is called reverse CAMP test because CAMP factor produced by S. agalactiae is used for the detection of Clostridium perfringens from other Clostridium species.
A CAMP positive Group B Streptococcus is streaked in the center of sheep blood agar, and Clostridium perfringens is streaked perpendicular to it. Following incubation at 37°C for 24-48 hours in anaerobic conditions, the “bow-tie” zone of enhanced hemolysis pointing towards Streptococcus agalactiae is seen. This is because of alpha toxin produced by Clostridium perfringens interacts with CAMP factor and produce synergistic hemolysis.
- Inoculate pure culture of CAMP positive S. agalactiae along the diameter of the blood agar plate by streaking.
- Suspected clostridial culture is streaked at right angle to the streak of S. agalactiae (not touching to the streak of S. agalactia).
- Incubate anaerobically at 37°C for 24hours.
- Observe for zone of hemolysis pointing toward S. agalactiae.
The positive reaction of Clostridium perfringens is shown by the “bow-tie” zone of enhanced hemolysis pointing towards Streptococcus agalactiae (group B).