<prompt> Double zone of hemolysis is seen in ?Staphylococcus areusStreptococcus pyogenesClostridium perfringensCorynebacterium diphtheriae  <response>: 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. Naeglers 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. 