This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Reverse CAMP test is positive for ? 
Select and explain. 
A. Streptococcus agalactiae, B. Listeria manocytogenes, C. Clostridium perfringens, D. Vibrio parahemolyticus
C: Clostridium perfringens
Answer: C: Clostridium perfringens 
Explanation: Ans. is 'c' i.e.,Clostridium perfringens CAMP positive- Area of increased hemolysis (arrow head) around staphylococcus streaks (by streptococcus agalactiae).CAMP test is also positive in Listeria monocytogenes, Reverse CAMP test is positive in Clostridium perfringens.Reverse CAMP test : It is used to differentiate Cl perfringens from other Clostridia. CAMP positive group 'B' streptococcus is streaked in Blood agar and Cl perfringens is streaked perpendicular to it. There is enhanced hemolysis (arrowhead) between the growth of Cl.