Submitted to: International Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2010
Publication Date: 9/1/2010
Publication URL: http://www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2209.pdf
Citation: Ibekwe, A.M., Papiernik, S.K., Grieve, C.M., Yang, C. 2010. Quantification of persistence of Escherichia coli O157:H7 in contrasting soils. Internationl Journal of Microbiology. Available: http://www.hindawi.com/journals/ijmb/2011/421379.html. Interpretive Summary: Suppression of human pathogens in agricultural soils and the subsequent prevention of spread into the food chain by contamination of produce must be realized by the adoption of best management practices. This will prevent contamination of preharvest fresh produce and achieved the delivery of microbiological safe produce to consumers. This study was conducted to determine the effects of preplant fumigation treatment on the survival of E. coli O157:H7 in two soils and the effects of indigenous bacterial populations on the survival of this pathogen. Sandy and clay soils were inoculated with E. coli O157:H7 then fumigated with methyl bromide and methyl iodide. Fumigation resulted in a significant decline in E. coli O157:H7 numbers during the first 10 days compared to the control, and thereafter, there were no differences between fumigated treatment and the control. Microbial species diversity was higher in clay soil than sandy soil and this resulted in higher initial decline in population in clay soil than in sandy soil. Therefore, soil systems with lower microbial community complexity may offer enhanced opportunities for E. coli O157:H7 survival. This research will benefit Scientists agricultural producers.
Technical Abstract: Persistence of Escherichia coli (E. coli) O157:H7 in the environment is a major concern to vegetable and fruit growers where farms and livestock production are in close proximity. The objectives were to determine the effects of preplant fumigation treatment on the survival of E. coli O157:H7 in two soils and the effects of indigenous bacterial populations on the survival of this pathogen. Real-time PCR 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). Ten days after fumigation, E. coli O157:H7 counts were significantly lower (P=.0001) in fumigated soils than in the non-fumigated. Direct comparison between MeBr and MeI within each soil indicated that these two fumigants showed similar impacts on E. coli O157:H7 survival. Microbial species diversity as determined by DGGE was significantly higher in clay soil than sandy soil and this resulted in higher initial decline in population in clay soil than in sandy soil. This study shows that if soil is contaminated with E. coli O157:H7, fumigation alone may not eliminate the pathogen, but may cause decrease in microbial diversity which may enhance the survival of the pathogen.