Double zone of hemolysis is seen in ?

Ans. is 'c' i.e., Clostridium perfringens Two impoant characteristic feature of Cl. perfringens are :? Target hemolysis (double zone hemolysis) on blood agar. It is a narrow zone of complete hemolysis by theta toxin which is surrounded by a wider incomplete hemolysis by alpha-toxin. Naegler's reaction detects alpha toxin (phospholipase or lecithinase C). When CL. perfringens is grown on a medium with the antitoxin spread on one half of the plate, colonies on the other half without the antitoxin will be surrounded by a zone of opacity. There will be no opacity around the colonies on the half of the plate with the antitoxin, due to the specific neutralisation of the alpha-toxin.