All are catalase positive Except
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
Shigella flexineri
Shigella boydii
Shigella dysentriae type I
Shigella sonnei
Bacteriology