DISTRIBUTION AND CHARACTERIZATION OF FECAL VEROTOXIN-PRODUCING ESCHERICHIA-COLI (VTEC) ISOLATED FROM HEALTHY CATTLE

Faecal swabs obtained from a random sample of 268 cows and 90 calves o n 19 Lugo farms were examined for verotoxin-producing Escherichia coli (VTEC). We found VTEC on 95% of the farms. The prevalence rates of VT EC infection in asymptomatic cows and calves were estimated to be 35 a nd 37%, respectively. The proportion of animals infected on each farm ranged from 0 to 100%. VTEC strains isolated from healthy cattle belon ged to 27 O serogroups; however, 57% (85 of 149) were of one of 8 sero groups (O2, O8, O22, O77, O82, O105, O113 and O171), Nearly 60% of the bovine VTEC strains belonged to serogroups that cause haemorrhagic co litis and haemolytic uraemic syndrome in humans. The VTEC were all non -O157:H7; 91% were eae-negative and 86% produced VT2 or VT1 and VT2. T hese characteristics are different from those of VTEC isolated from ca lves with diarrhoea.