Detection and characterisation of O157:H7 and non-O157 Shiga toxin-producing Escherichia coli in wild boars

Abstract

The aim of this work was to determine the prevalence and characteristics of Escherichia coli O157:H7 and non-O157 Shiga toxin-producing E. coli (STEC) in free-ranging wild boars killed during the hunting season in southwest Spain. Faecal samples from 212 wild boars (Sus scrofa) were collected and examined for STEC. Characterisation of isolates was performed by PCR, serotyping, phage typing, and pulsed-field gel electrophoresis (PFGE). E. coli O157:H7 and non-O157 STEC were isolated from 7 (3.3%) and 11 (5.2%) animals, respectively, and the resulting 19 isolates were characterised. The PCR procedure indicated that 4 isolates carried the stx1 gene, 12 carried the stx2 gene, and 1 contained both of these genes. The ehxA, eae, and saa genes were detected in 13, 8, and 1 of the isolates, respectively. The eae-positive isolates comprised the types eae-γ1 and eae-ζ. The isolates belonged to 11 O:H serotypes, including 4 new serotypes not previously reported within STEC strains, and the majority of them were from serotypes previously associated with human infection. E. coli O157:H7 isolates belonged to phage types associated with severe human illness: PT14, PT34, and PT54. Indistinguishable PFGE types were found in E. coli O157:H7 isolates recovered from a wild boar and from a human patient with diarrhoea living in the same geographic area.