Epidemiology of Escherichia coli serogroups O26, O103, O111 and O145 in very young ('bobby') calves in the North Island, New Zealand

Abstract

The prevalence and spatial distribution of Escherichia coli serogroups O26, O103, O111 and O145 in calves <7 days old in New Zealand and their relationship with serum IgG, weight and sex was determined by collecting recto-anal mucosal swabs (RAMS) (n = 299) and blood samples (n = 299) from two slaughter plants in the North Island. Real-time PCR of RAMS enrichment cultures revealed that 134/299 samples were positive for O26, 68/299 for O103 and 47/299 for O145, but none were positive for O111. Processing of positive enrichment cultures resulted in 49 O26, four O103 and five O145 isolates. Using multiplex PCR 25/49 (51%) O26 isolates were positive for stx1, eae, ehxA, 17/49 (34·7%) for eae, ehxA and 7/49 (14·2%) for eae only. All O103 and O145 isolates were positive for eae, ehxA only. O26 isolates were grouped into four clusters (>70% similarity) using pulsed field gel electrophoresis. Mapping of the farms showed the presence of farms positive for O26, O103 and O145 in three important dairy producing regions of the North Island. Calves positive for O103 were more likely to be positive for O26 and vice versa (P = 0·04). Similarly, calves positive for O145 were more likely to be positive for O103 and vice versa (P = 0·03). This study demonstrates that non-O157 E. coli serogroups of public health and economic importance containing clinically relevant virulence factors are present in calves in the North Island of New Zealand.