[Enterotoxigenic Escherichia coli K99+, serotype 08:K25, produce cytotoxic necrotizing factor CNF1 and alpha-hemolysin].

A total of 54 K99+ and/or F41+ Escherichia coli strains isolated of calves and piglets with diarrhoea in different countries were investigated for production of heat-labile (LT) and heat-stable (STa) enterotoxins, verotoxins (VT1 and VT2), cytotoxic necrotizing factors (CNF1 and CNF2), alpha-haemolysin (Hly) and enterohaemolysin (EntHly). Fifty-one (94%) strains were STa+, two (4%) were STa+CNF1+Hly+ and one (2%) was not toxigenic. The two STa+CNF1+Hly+ E. coli strains expressed the K99 intestinal colonization factor and belonged to serotype O8:K25. The majority of STa-producing E. coli were K99+ and F41+ and belonged to serotypes O9:K(A)35, O101:K(A)28 and O101:K(A)30. All enterotoxigenic strains assayed in this study were negative for expression of the Att25, Vir and B23 adhesins recently detected in E. coli that cause infections in calves.