Meat Industry Services - Effect of testing regimes on E. coli O157 isolation

Summary

Meat destined for export to the US and other countries must be tested and deemed free of E. coli O157 prior to being released into commerce. DAFF coordinates a testing program within Australia aimed at limiting the release of contaminated meat into export markets. Despite this, there has been a recent increase in the rejection rate of Australian beef from the US as a result of POE testing. As the US is a major beef trading partner of Australia, the increased rejection rate will reduce the confidence in the Australian beef supply and may lead to a contraction of market share in the US. A greater understanding of how individual components of the various testing regimes used in Australia affect the ability to isolate E. coli O157 will enable the identification of factors that result in a low conversion rate of potential positives to presumptive positives.
The current approach for testing for E. coli O157 in meat relies on first performing a screening test on an enrichment broth which contains a mixture of bacteria. Samples which test positive for the appropriate targets are typically sent to one of two commercial laboratories for confirmation. DAFF currently approves a number of methods for E. coli O157 testing and there is increasing concern that testing regimes may be impacting on the likelihood of isolating the target organism if it is present in the test sample. More specifically, it is hypothesised that the type of enrichment broth used, time between screening and the commencement of confirmation, and storage temperatures of broths prior to confirmation may affect the ability to isolate the target organism.
A greater understanding of the issues associated with failure to isolate E. coli O157 from positive screening tests will provide processors with information that can be used to: - Determine if transport (time and temperature) impacts the recovery of E. coli O157 - Provide guidance on the most appropriate and efficient testing and transport strategy for potential positive samples to confirmation laboratories - Continue to have a favourable trading position in international markets.