a1 mEpiLab, Hopkirk Research Institute, Massey University, Palmerston North, New Zealand
a2 AgResearch Ltd, Grasslands Research Centre, Palmerston North, New Zealand
a3 Enteric Reference Laboratory, ESR-NCBID, New Zealand
The objective of this study was to determine the distribution of Shiga toxin-producing Escherichia coli (STEC) virulence markers (stx1, stx2, eae, ehxA) in E. coli strains 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 detect stx1, stx2, eae and ehxA genes. The most common combination of virulence markers were eae, ehxA (n = 35) followed by eae (n = 9). In total, STEC and atypical enteropathogenic E. 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 using XbaI 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.
(Received May 30 2013)
(Revised September 30 2013)
(Accepted January 07 2014)
(Online publication February 06 2014)