Occurrence of verocytotoxin-producing Escherichia coli in dairy and meat processing environments

Abstract

From June 1999 to June 2000, 480 environmental swabs were collected from two abattoirs in Northern Ireland. In addition, from July 1999 to July 2000, 420 samples originating from raw cow's milk were collected from two Northern Ireland dairies. All samples were examined for the presence of verocytotoxin-producing Escherichia coli (VTEC) O157 with the use of selective enrichment in tryptone soya broth (TSB) and double-strength MacConkey broth purple (MBP) followed by immunomagnetic separation and selective plating onto sorbitol MacConkey agar supplemented with cefixime tellurite. Non-O157 VTEC was detected by selective enrichment in TSB-MBP and plating on MacConkey agar. A multiplex polymerase chain reaction assay was also used to detect the presence of the VT1, VT2, and eae genes. Two (0.42%) of the 480 abattoir samples tested positive for VTEC; one isolate carried the VT2 gene only, and the other carried both the VT2 and the eae genes. Nine (2.14%) of the 420 dairy samples tested positive for VTEC; four carried the VT2 gene only, four carried both the VT2 and the eae genes, and one carried both the VT1 and the eae genes. These results indicate that the incidence of VTEC was low in the dairy and meat processing environment samples tested, and this finding may help to explain the low incidence of VTEC reported for the local human population.