Methods for the isolation of water-borne Escherichia coli O157

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Abstract
Aims: To develop improved methods for the detection of Escherichia coli O157 from water and sediments. Methods and Results: The effects of different broth enrichment media (unsupplemented tryptic soya broth, tryptic soya broth with antibiotics, and gram-negative broth), incubation durations (5 and 24 hrs), incubation temperatures (37 and 44.5°C) and the use of immunomagnetic separation (IMS) on the sensitivity of E. coli O157 detection were evaluated on artificially and naturally-contaminated water and sediment samples. The sensitivity of recovery of E. coli O157 from samples was dependent upon the media composition, temperature duration of incubation and the use of IMS. Conclusions: Use of high temperature (44.5°C) incubation for 24 hrs in unsupplemented tryptic soya broth and the use of IMS improved the sensitivity of E. coli O157 culture from water and sediment samples. Significance and Impact of the Study: The methods described can be used to increase the sensitivity of E. coli O157 detection from water and sediments.