Methods for the isolation of water-borne Escherichia coli O157

Aims: To develop improved methods for the detection of Escherichia coli O15 7 from water and sediments. Methods and Results: The effects of different broth enrichment media (unsup plemented tryptic soya broth, tryptic soya broth with antibiotics, and gram -negative broth), incubation durations (5 and 24 hrs), incubation temperatu res (37 and 44.5 degreesC) and the use of immunomagnetic separation (IMS) a n the sensitivity of E. coli O157 detection were evaluated on artificially and naturally-contaminated water and sediment samples. The sensitivity of r ecovery of E. coli O157 from samples was dependent upon the media compositi on, temperature duration of incubation and the use of IMS. Conclusions: Use of high temperature (44.5 degreesC) incubation for 24 hrs in unsupplemented tryptic soya broth anti the use of IMS improved the sensi tivity of E. coli O157 culture from mater 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 vi;ater and sedimen ts.