PREVALENCE AND CHARACTERIZATION OF ENTERO HEMORRHAGIC ESCHERICHIA-COLI ISOLATED FROM HEALTHY CATTLE AND PIGS SLAUGHTERED IN SANTIAGO, CHILE

As a contribution to the epidemiology of SHU in Chile, this work was f ocused on cattle and pigs as a possible reservoir of EHEC. This was ac hieved by analyzing E. coli isolates from faecal samples of healthy an imals slaughtered in two abattoirs in Santiago. EHEC strains were iden tified by DNA hybridization with specific gene probes for Shiga-like t oxin I (SLTI) and II (SLTII). Positive strains were hybridized with sp ecific gene probes for fimbrial adhesin and eae factor, serogrouped an d examined for sorbitol fermentability. Among the 136 steers and 120 p igs studied, 39 (28.7%) and 82 (68.3%) were found to carry EHEC strain s, respectively. Of the 40 bovine strains that hybridized with two SLT DNA probes, 29 (72.5%) hybridized with only SLTI probe, 6 (15%) hybri dized with only SLTII probe and 5 (12.5%) hybridized with both SLTI an d SLTII probes. Only 6 (15%) of the 40 EHEC hybridized with fimbrial a dhesin probe and 14 (35%) hybridized with eae probe. An important numb er of strains (14/40) belonged to serogroups O157, O26 and O111; serog roups also commonly isolated from SHU cases in Chile. One steer was fo und to carry two EHEC strains of different serogroups. 50% of EHEC wer e sorbitol positive, irrespective of the O serogroup or genotypic prof ile. Of the 82 pig strains, the predominant cytotoxic profile was SLTI -SLTII (68.3%); only 35 (42.7%) hybridized . with fimbrial adhesin pro be. An important number of strains (80/82) hybridized with eae probe. The serogroups found were: O157, O26, O111, O114, O119, O126, O127, O1 28, O142 and O158. Approximately 50% of EHEC strains were sorbitol pos itive, O157 included. Results obtained in this study strongly suggest that cattle and pigs in Chile are a reservoir of EHEC associated with diseases in humans.