Distribution ofEscherichia colistrains harbouring Shiga toxin-producingE. coli(STEC)-associated virulence factors (stx1, stx2, eae, ehxA) from very young calves in the North Island of New Zealand

Abstract

SUMMARYThe objective of this study was to determine the distribution of Shiga toxin-producingEscherichia coli(STEC) virulence markers (stx1,stx2,eae,ehxA) inE. colistrains isolated from young calves aged fewer than 7 days (bobby calves). In total, 299 recto-anal mucosal swabs were collected from animals at two slaughter plants and inoculated onto tryptone bile X-glucuronide and sorbitol MacConkey agar supplemented with cefixime and potassium tellurite. Isolates were analysed using multiplex polymerase chain reaction to detectstx1,stx2,eaeandehxAgenes. The most common combination of virulence markers wereeae, ehxA(n = 35) followed byeae(n = 9). In total, STEC and atypical enteropathogenicE. coli(aEPEC) were isolated from 8/299 (2·6%) and 37/299 (12·3%) calves, respectively. All the isolates could be assigned to 15 genotype clusters with >70% similarity cut-off usingXbaI pulsed-field gel electrophoresis. It may be concluded that healthy calves from the dairy industry are asymptomatic carriers of a diverse population of STEC and aEPEC in New Zealand.