Zoonotic infections infections in livestock and the risk to public health - Poster Abstract

Improved isolation techniques for Escherichia coli O157 in food

I D Ogden et al

The advent of immunomagnetic separation (IMS) in 1994 dramatically increased the isolation rate of Escherichia coli O157 from food. Since that time, IMS protocols have differed widely and rapid end point detection methods have sought to bring the total assay time to within the working day. This paper describes a series of modifications to the original IMS method which have improved the detection of target cells. Low numbers of sub-lethally injured E. coli O157 in the presence of high numbers of healthy competing micro-organisms in mince, cheese, apple juice and pepperoni were tested. IMS assays routine use 1ml of enriched sample but this study indicates a nine-fold increase in target numbers when 10ml volumes are tested. IMS beads are typically plated onto selective agar from which suspect colonies are confirmed by latex agglutination. An alternative detection method using a modified microsphere coagulation ELISA incorporating Russell's viper venom (capable of detecting 100 organisms) is also described.

Research Fellow

01224 551132, fax 01224 685604, e-mail i.ogden@abdn.ac.uk

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