Characterization of Shiga toxin-producing Escherichia coli isolated from dairy cows in Argentina


Nora L. Padola, Fac. Cs. Veterinarias-UNCPBA, Pinto 399 (7000), Tandil, Argentina. E-mail:


Aims:  To feno-genotypically characterize the Shiga toxin-producing Escherichia coli (STEC) population in Argentinean dairy cows.

Methods and Results:  From 540 STEC positive samples, 170 isolates were analyzed by multiplex PCR and serotyping. Of these, 11% carried stx1, 52%stx2 and 37%stx1/stx2. The ehxA, saa and eae were detected in 77%, 66% and 3%, respectively. Thirty-five per cent of strains harboured the profile stx1, stx2, saa, ehxA and 29%stx2, saa, ehxA. One hundred and fifty-six strains were associated with 29 different O serogroups, and 19 H antigens were distributed among 157 strains. STEC O113:H21, O130:H11 and O178:H19 were the most frequently found serotypes. The STEC O157:H7 were detected in low rate and corresponded to the stx2+, eae+, ehxA+ virulence pattern.

Conclusions:  We detected a diversity of STEC strains in dairy cattle from Argentina, most of them carrying genes linked to human disease.

Significance and Impact of the study:  The non-O157 STEC serotypes described in this study are associated worldwide with disease in humans and represent a risk for the public health. For this, any microbiological control in dairy farms should be targeted not only to the search of O157:H7 serotype.