Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: September 20, 2003
Publication Date: November 20, 2003
Citation: Ibekwe, A.M., Watt, P.M., Papiernik, S.K. 2003. Impact of fumigants on soil bacteria and E. coli O157:H7. (CD-ROM) American Society of Agronomy Annual Meeting. Denver, CO, November, 2003.
Agricultural soils are typically fumigated to provide effective control of nematodes and soil-borne pathogens in preparation for planting of high value cash crops. In the past, animal manure has been applied to agricultural land with little or no regulation. Many groups have voiced concerns about the safety of land application of manure and their potential for food and water contamination by Escherichia coli (E. coli) O157:H7 from agricultural runoffs. In this study, a multiplex fluorogenic PCR assay was used in conjunction with plate counts to quantify E. coli O157:H7 in soil after fumigation with methyl bromide (MeBr) and methyl iodide (MeI). Primers and probes were designed to amplify and quantify the Shiga-like toxin 1 (stx1) and 2 (stx2) genes and the intimin (eae) gene of E. coli O157:H7 in a single reaction. A direct correlation was determined between the fluorescence threshold cycle (CT) and the starting quantity of E. coli O157:H7 DNA. A detection limit of approximately 6.4 X 102 CFU ml-1 E. coli O157:H7 based on plate counts was determined. Both fumigants were effective in reducing pathogen concentrations in soil before planting, with MeBr having the highest impact on soil microbial communities.