Detection of Escherichia coli O157:H7 in soil and water using multiplex PCR

Aims: To evaluate the suitability of a multiplex PCR-based assay for sensitive and rapid detection of Escherichia coli O157:H7 in soil and water. Methods and Results: Soil and water samples were spiked with E. coli O157:H7 and subjected to two stages of enrichment prior to multiplex PCR. Detection sensitivities were as high as 1 cfu ml(-1) drinking water and 2 cfu g(-1) soil. Starvation of E. coli O157:H7 for 35 d prior to addition to soil did not affect the ability of the assay to detect initial cell numbers as low as 10 cfu g(-1) soil. Use of an 8-h primary enrichment enabled detection of as few as 6 cfu g(-1) soil, and 10(4) cfu g(-1) soil with a 6-h primary enrichment. When soil was inoculated with 10(5) cfu g(-1), the PCR assay indicated persistence of E. coli O157:H7 during a 35 d incubation. However, when soil was inoculated with lower numbers of pathogen, PCR amplification signals indicated survival to be dependent on cell concentration. Conclusions: A multiplex PCR-based assay, in combination with an enrichment strategy enabled sensitive and rapid detection of E. coli O157:H7 in soil and water. Significance and Impact of the Study: The ability to sensitively detect E. coli O157:H7 in environmental material within one working day represents a considerable advancement over alternative more time-consuming methods for detection of this pathogen.