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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
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Double zone of hemolysis is seen in -
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The correct answer is  Ans. is 'c' i.e., Clostridium perfringens o Two important 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.