Detection of enterohaemorrhagic Escherichia coli O157:H7 in minced beef using immunomagnetic separation.

Enterohaemorrhagic Escherichia coli (EHEC) O157:H7 has been recently recognized as a human pathogen associated with haemorrhagic colitis and haemolytic uraemic syndrome. Most outbreaks of haemorrhagic colitis resulted from the consumption of undercooked minced beef or raw milk. Dairy cattle have been identified as a reservoir of EHEC O157: H7. In this study E. coli O157 specific antibody, coated on magnetic beads, was used to concentrate and release EHEC O157:H7 from meat samples. A survey of retail fresh minced beef and hamburger samples using this procedure revealed that 3 (5%) of 58 beef samples were positive for EHEC O157:H7. Two of the strains produced both VT1 and VT2 verotoxins, and one produced only VT2. Immunomagnetic separation is a sensitive and simple technique for the isolation of E. coli O157 from food, and could be useful for a further elucidation of the epidemiology of this organism. The relatively high prevalence of EHEC O157:H7 in beef samples may constitute a risk for public health. Thus, a suitable epidemiologic control and effective methods of prevention should be applied.