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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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All are catalase positive Except
assistant
The correct answer is  S.dysenteriae (subgroup A): This species of mannitol non-fermenting bacilli consists of ten serotypes. It is indole negative and is the only member of the family that is always catalase-negative. S.flexineri, S.boydii, and S.sonnei are catalase positive. Ref: Textbook of microbiology; Aanthanarayan and paniker's; 10th Edition; Pg:292