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E.coli remains the indicator of choice for the detection of fecal contamination in waterand many methodologies are employed. Until relatively recently, methods were basedupon membrane filtration or most probable number techniques and isolates required"confirmation" using phenotypic tests. Application of PCR to the identification ofisolates growing on membranes has also been used.This study conducted an examination of over 6000 isolates of E.coli isolated from waterusing a variety of phenotypic and genotypic tests. The results of these studies showedthat the traditional confirmatory test, based on production of indole from tryptophan at44C was inaccurate. In fact, using the International Standards Organization procedurefor the detection of E.coli in drinking water resulted in a false positive rate ofapproximately 30%. These organisms were phenotypically identified as Klebsiellaoxytoca. Subsequent molecular analysis using PCR or in situ hybridization with anE.coli-specific probe clearly showed that these organisms were not E.coli. Testing theability of these organisms to produce the enzyme -D-glucuronidase also clearlydistinguished them from E.coli. Includes table.

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Edition: Vol. - No. Published: 11/01/2006 Number of Pages: 2File Size: 1 file , 350 KB