An eight-month study of a population of verocytotoxigenic Escherichia coli (VTEC) in a Scottish cattle herd

Aims: Strains of Verocytotoxin-producing Escherichia coli (VTEC) from Scottish beef cattle on the same farm were isolated during four visits over a period of eight months. Characteristics of these strains were examined to allow comparisons with strains of VTEC associated with human infection. Methods and Results: Strains were characterized to investigate the relationship between these bovine isolates with respect to serotype, Verocytotoxin (VT) type, intimin-type, and presence or absence of the enterohaemolysin genes. VT genes were detected in 176 of 710 (25%) faecal samples tested using PCR, although only 94 (13%) VTEC strains were isolated using DNA probes on cultures. Forty-five different serotypes were detected. Commonly isolated serotypes included O128ab:H8, O26:H11 and O113:H21. VTEC O26:H11 and O113:H21 have been associated with human disease. Strains harbouring the VT2 genes were most frequently isolated during the first three visits to the farm and those with both VT1 and VT2 genes were the major type during the final visit. Of the 94 strains of non-O157 VTEC isolated, 16 (17%) had the intimin gene; nine had the gene encoding β-intimin and seven strains had an η/ζ-intimin gene. Forty-one (44%) of 94 strains carried enterohaemolysin genes. Conclusions: Different serotypes and certain transmissible characteristics, such as VT-type and the enterohaemolysin phenotype, appeared to be common throughout the VTEC population at different times. Significance and Impact of the Study: Detailed typing and subtyping strains of VTEC as described in this study may improve our understanding of the relationship between bovine VTEC and those found in the human population.