Recovery of Escherichia coli 0157:H7 from mixed suspensions: evaluation and comparison of pre-coated immunomagnetic beads and direct plating.

: Escherichia coli O157:H7 has become an important enteropathogen, causing sporadic outbreaks of haemorrhagic colitis. However, it has not so far been isolated from suspect foods, which may be due to low numbers, sub-lethal injury, or overgrowth by other organisms. Immunomagnetic separation could provide an answer to these problems. The technique utilises antibody-coated magnetic polymer beads and is considered fast, safe, sensitive and reproducible. Commercially produced polymer beads coated with a polyclonal antibody were standardised and compared with direct plating to maximise recovery of Esch. coli O157:H7 from mixed suspensions. An increase in sensitivity was found, but this was offset by a loss of specificity.