HEMOLYTIC ESCHERICHIA-COLI STRAINS ISOLATED FROM STOOLS OF HEALTHY CATS PRODUCE CYTOTOXIC NECROTIZING FACTOR TYPE-1 (CNF1)

A total of 159 Escherichia coli colonies isolated from the stools of 23 healthy cats were studied for production of cr-haemolysin (Hly), enterohaemolysin (EntHly), cytotoxic necrotizing factors (CNF1 and CNF2), verotoxins (VT) and heat-labile enterotoxin (LT). Hly(+)CNF1(+),Hly(+)CNF2(+),Hly(+)VT(+) and Hly(+) E. coli colonies were isolated from 12 (48%), 1 (4%), 1 (4%) and 2 (8%) respectively of the cats sampled. None of the 159 E. coli colonies produced LT or EntHly. Nine of 12 Hly(+)CNF1(+) strains from the cats belonged to serogroup O6 and eleven to serotypes (O4:K?:H5 or H-, O6:K13:H1, O6:K53:H-, O6:K53:H1, O6:K53:H7 and O6:K14:H31) found among Hly(+)CNF1(+) E. coli that cause urinary tract infections and sepsis in humans. Furthermore, 10 Hly(+)CNF1(+) strains from the cats expressed the mannose-resistant haemagglutination (MRHA) type III. By contrast, the majority of nontoxigenic E. coli strains were MRHA negative and belonged to different O groups. We conclude that cats are a important reservoir of Hly(+)CNF1(+) E. coli strains that possess similar characteristics to strains that can cause extraintestinal infections in humans and that Hly(+) E. coli from cats usually do not produce shiga-like toxins with cytotoxic activity on Vero cells.