A survey of the prevalence of Escherichia coli O157 in raw meats, raw cow's milk and raw-milk cheeses in south-east Scotland

Abstract

2429 samples of foodstuffs were examined for the presence of verocytotoxigenic Escherichia coli O157 (VTEC O157) by means of immunomagnetic separation (IMS) over a 2-year period commencing April 1997. Specimens comprised 1190 raw meats, 500 raw milks and 739 raw-milk cheeses. The meat and cheese samples were purchased from retail premises in south-east Scotland; raw milk samples were obtained directly from farms. In addition, total E. coli counts were performed on milk and cheese samples, and the pH of cheese specimens measured. The water activity ( A w) was also measured for a representative sample of each cheese type, and for all of the samples with high levels of E. coli. VTEC O157 was isolated from two samples of beef burger, both manufactured on the premises of the same butchers shop. Control studies with artificially inoculated foodstuffs demonstrated a sensitivity of detection of <5 organisms 25 g −1. These findings, which contrast with the results of similar studies elsewhere in the UK, suggest that other sources of infection may be important in explaining the high rates of infection with this organism in south-east Scotland.