The production of verotoxin was investigated in 1127 Escherichia coli isolated from 243 dairy cattle, water for human and animal consumption, and milk samples from 60 dairy farms from Pelotas-Brazil, from December of 1999 to December of 2000, to determine the prevalence of verotoxigenic E. coli (VTEC) in farms, to detect the presence of serotypes involved in human infections and to identify potential risk factors for animal infection. Vero cell assay was used to detect toxins in culture supernatants from E. coli isolated. VTEC was isolated in 95% (57/60) from farms and in 49% (119/243) from cattle, 5% (3/60) from water of human consumption, in 8.35% (5/60) from water animal consumption and 5% (3/60) from milk samples. The prevalence of cattle infected for each farm ranged from 0 to 100%. VTEC belonging to serogroups O157, O91 and O112, which include strains responsible for cases of hemorrhagic colitis and hemolytic uremic syndrome in humans, were isolated from 7 (2.9%) out of 243 cattle. Risk factors for contamination, such as amount of rain, farm size and cattle number, influenced cattle prevalence rate. These results suggest that VTEC is widely distributed among dairy cattle in the region surveyed and includes organisms from serogroups pathogenic for humans.
Escherichia coli; verotoxins; VTEC; cattle
