Phenotypic and genotypic traits of Shiga toxin-producing Escherichia coli strains isolated from beef cattle from Parana State, southern Brazil

Aims: To investigate the prevalence and characteristics of Shiga toxin-producing Escherichia coli (STEC) in cattle from Parana State, southern Brazil. Methods and Results: One hundred and seven faeces cattle samples were cultured on Sorbitol-MacConkey agar. Escherichia coli colonies were tested for production of Shiga toxin using Vero-cell assay. A high prevalence (57%) of STEC was found. Sixty-four STEC were serotyped and examined for the presence of stx(1), stx(2), eae, ehxA and saa genes and stx(2) variants. The isolates belonged to 31 different serotypes, of which three (O152:H8, O175:H21 and O176:H18) had not previously been associated with STEC. A high prevalence of stx(2)-type genes was found (62 strains, 97%). Variant forms found were stx(2), stx(2c), stx(2vhb), stx(2vO111v/OX393) and a form nonclassifiable by PCR-RFLP. The commonest genotypes were stx(2)ehxA saa and stx(1)stx(2)ehxA saa. Conclusions: A high frequency of STEC was observed. Several strains belong to serotypes previously associated with human disease and carry stx(2) and other virulence factors, thus potentially representing a risk to human health. Signifance and Impact of the Study: This is the first study of STEC in Parana State, and its findings emphasize the need for proper cattle handling to prevent human contamination.