Validation of low volume enrichment for rapid E. coli O157 screening tests

Summary

Testing of beef destined for use in ground beef products for the presence of Escherichia coli O157:H7 has become an important cornerstone of control and verification activities within many meat supply chains.
Validation of the ability of methods to detect low levels of E. coli O157:H7 is critical to confidence in test systems.
Many rapid methods have been validated against standard cultural methods for 25g samples.
In this study, a number of previously validated enrichment broths and commercially available test kits were validated for the detection of low numbers of E. coliO157:H7 in 375g samples raw ground beef component matrices using 1 liter of enrichment broth (large sample:low volume enrichment protocol).
Standard AOAC methods for 25g samples in 225ml of enrichment broth using the same media, incubation conditions and test kits were used as reference methods.
No significant differences were detected in the ability of any of the tests to detect low levels of E. coli O157:H7 in samples of raw ground beef components when enriched according to standard or large sample:low volume enrichment protocols.
This report documents the results of the study according to National Association of Testing Authority's Australia validation criteria.
The manuscript in Appendix 3 was subsequently published and may be cited as:
Imtiaz Ahmed, Denise Hughes, Ian Jenson and Tass Karalis (2009) Validation of low volume enrichment protocols for detection of Escherichia coli O157 in raw ground beef components using commercial kits. Journal of Food Protection. 72(3) 669-673 .