Submitted to: Annual Quantitative Polymerase Chain Reaction (PCR) Meeting
Publication Type: Abstract Only
Publication Acceptance Date: December 1, 2005
Publication Date: February 10, 2006
Citation: Ibekwe, A.M., Grieve, C.M. 2006. Real-time pcr quantification of persistence of escherichia coli o157:h7 in soil impacted by fumigations. (Abstract) CD-ROM. Annual Quantitative Polymerase Chain Reaction (PCR) Meeting. Technical Abstract: Survival of Escherichia coli O157:H7 in the environment is a major concern to many municipalities where human and livestock live in close proximity to each other due to rapid urbanization. The major objectives of this study were to determine the effects of soil type and fumigant treatment on the survival of E. coli O157:H7. Real-time PCR (Polymerase Chain Reaction) and plate counts were used to quantify the survival of E. coli O157:H7 in two contrasting soils after fumigation with methyl bromide (MeBr) and methyl iodide (MeI). Real-time PCR assays were designed to amplify the stx1, stx2, and the eae genes of E. coli O157:H7. The probes were incorporated into real-time PCR containing DNA extracted from soil, rhizosphere, and phyllosphere samples. The detection limit for E. coli O157:H7 quantification by real-time PCR was 2.4 x 103 CFU ml-1 of starting DNA in soil, rhizosphere, and, phyllosphere samples. Ten days after fumigation, E. coli O157:H7 counts were significantly lower (P = 0.0001) in fumigated soils (normal application rate) than in the non-fumigated. There was no significant effect of fumigants on pathogen counts after the initial 10 d period in most of the treatments. Direct comparison between MeBr and MeI within each soil indicated that these two fumigants showed similar impacts on E. coli O157:H7 survival. However, survival of E. coli O157:H7 was significantly greater in sandy soil than in clay soil during the short duration (50 d) of these experiments in a growth chamber. During the long term laboratory microcosm experiment (90 d) survival was significantly higher in the clay soil due to higher moisture content towards the end of the experiment. This study shows for the first time that if soil is contaminated with E. coli O157:H7, fumigation alone may not eliminate the pathogen.