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Title: Quantification of survival of Escherichia coli 0157:H7 on Plants affected by Contaminated Irrigation Water

item Ibekwe, Abasiofiok - Mark
item Shouse, Peter
item Grieve, Catherine

Submitted to: Engineering in Life Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2006
Publication Date: 11/28/2006
Citation: Ibekwe, A.M., Shouse, P.J., Grieve, C.M. 2006. Quantification of survival of Escherichia Coli 0157:H7 on Plants affected by Contaminated Irrigation Water. Engineering in Life Sciences. Vol. 6:566-572

Interpretive Summary: Contaminated irrigation water is one of the most common vehicles by which E. coli O157:H7 may be introduced into the environment, and flood irrigation with surface water contaminated with cattle feces may be the fastest method for E. coli O157:H7 contamination from surface water to crops. Data from our study showed that E. coli O157:H7 survived best and remained culturable for a longer period of time in the rhizophere of plants than in soil. Survival was greater and longer in clay soil than in sandy soil. This shows that the rhizosphere and soil type had significant influence on the survival of E. coli O157:H7 in soil and on plants. Soil type may also have a significant influence on the survival of the pathogen after many weeks compared to the first few days after the initial contamination event. Our study showed E. coli O157:H7 survived longer than 45 days in soil, roots and leaf surfaces and this may have significant implications for waste management especially in areas where produce are grown.

Technical Abstract: Enterohemorrhagic E. coli O157: H7 (EHEC) is a major foodborne pathogen capable of causing diarrhea and vomiting, with further complications such as hemolytic-uremic syndrome (HUS). The aim of this study was to use real-time PCR method to quantify the survival of Escherichia coli O157:H7/pGFP in phyllosphere (leaf surface), rhizosphere (volume of soil tightly held by plant roots), and non-rhizosphere soils (sand and clay) irrigated with contaminated water and compare the results obtained between real-time PCR method and conventional plate counts. Real-time PCR probe was designed to hybridize with the (eae) gene of E. coli O157:H7. The probe was incorporated into real-time PCR containing DNA extracted from the phyllosphere, rhizosphere, and non-rhizosphere soils irrigated with water artificially contaminated with E. coli O157:H7. The detection limit for E. coli O157:H7 quantification by real-time PCR was 2300 cells in the rhizoshere and phyllosphere samples. E. coli O157:H7 survived longer in rhizosphere soil than the non-rhizosphere soil. The concentration of E. coli O157:H7 in rhizosphere soils was more than10000 CFU g/l in both soils at day 12 based on both plate count and real time PCR, with the clay soil significantly higher than the sandy soil. Our data showed that E. coli O157H:7 can survive in the environment for more than 50 days, and this may pose some risk for both animal and human infection and provides a very significant pathway for pathogen recontamination in the environment.