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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPING PROCESSING INTERVENTION TECHNOLOGIES

Location: Food Safety and Intervention Technologies

Title: Influence of mycorrhizal fungi (glomus intraradices) on survival of Salmonella and E.coli 0157:H7 in soil and translocation into romaine lettuce roots and shoot

Authors
item Gurtler, Joshua
item Nicholson, April -
item Douds, David
item Niemira, Brendan

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 6, 2012
Publication Date: July 22, 2012
Citation: Gurtler, J., Nicholson, A., Douds, D.D., Niemira, B.A. 2012. Influence of mycorrhizal fungi (glomus intraradices) on survival of Salmonella and E.coli 0157:H7 in soil and translocation into romaine lettuce roots and shoot. Meeting Abstract. International Association of Food Protection Annual Meeting, Providence. Rhode Island., July 2012.

Technical Abstract: Modern agriculture practices disrupt the natural symbiotic relationship that arbuscular mycorrhizal (AM) fungi have with most vegetable plants, which may affect translocation of human pathogens into the plant and/or survival in the soil. AM-fungi are frequently utilized in organic farming to improve plant productivity, soil quality and to increase drought resistance. The influence of AM-fungi (AMF) on survival of Salmonella and E. coli O157:H7 (EHEC) in soil and translocation into plant roots and shoot was determined. Six-week-old Romaine lettuce plants (with or without AMF [Glomus intraradices]) were inoculated (8 ml per plant) with composite suspensions of Salmonella or EHEC (8 log CFU/plant). Samples were taken one day following inoculation and then weekly up to 22 days. Samples were plated on XLT4PN and tcSMACPN. Pre-enrichments were made in TSBPN, while secondary enrichments were in TTPN for Salmonella and a novel TSBselect broth for EHEC. Salmonella and EHEC both internalized Romaine roots and shoots for up to 22 days following inoculation. Overall, there was little difference in pathogen populations between AMF-positive and AMF-negative roots, shoots, and soil. This is in contrast to results obtained from previous studies using a leek model. Salmonella populations were higher than EHEC (p less than 0.05) for 63% of all root and shoot samples; while final populations of the two pathogens in the soil at day 22 were ca. 4.3 and 1.2 log CFU/g, respectively. Selective enrichment samples (96%) for plant tissue were positive for Salmonella on day 22, while only 29% of EHEC enrichments were positive. Soil samples (100%) were positive for Salmonella by selective enrichment, and 83% were positive for EHEC by day 22. These results are the first to suggest that AM-fungi do not influence the internalization of pathogens in Romaine seedlings, which provides some assurance of the safe application of AMF in modern agricultural practices.

Last Modified: 4/23/2014
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