<prompt> All are catalase positive ExceptShigella flexineriShigella boydiiShigella dysentriae type IShigella sonnei  <response>: 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 panikers; 10th Edition; Pg:292 