ARS | Publication request: Survival of non-pathogenic E. coli and E. coli O157:H7 in Delmarva field plots amended with animal manure

Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: March 6, 2012
Publication Date: July 22, 2012
Citation: Cotton, C., Hashem, F., Jones, K., Sharma, M., Millner, P.D. 2012. Survival of non-pathogenic E. coli and E. coli O157:H7 in Delmarva field plots amended with animal manure. International Association for Food Protection. [abstract].

Technical Abstract: Introduction: Land application of raw animal manure to enhance soil productivity may pose a food safety risk from pathogenic microorganisms that survive and contact fresh produce grown on the soils. The presence of pathogens in fresh produce has resulted in several outbreaks of human gastroenteritis that have been linked to the consumption of contaminated fresh produce. Purpose: Evaluate and compare the survival and persistence of a multi-strain cocktail of non-pathogenic E. coli (Ec) and attenuated E. coli O157:H7 (attO157) as influenced by the application of poultry litter (PL) or dairy manure (DM) on field plots in the Delmarva peninsula. Methods: A field experiment comprising eight treatments with four replications was conducted in Othello soil at the University of Maryland Eastern Shore Ag Research Farm. Soil plots were individually amended with or without BL or DM in late fall. Individual plots, except controls, received spray inoculum containing three rifampicin-resistant (RifR) strains of Ec and two RifR strains of attO157 grown in dairy manure extract were sprayed onto plots as a single inoculum at either low, 5x10^6 CFU/sq. m., or high, 5x10^8 CFU/sq. m., cell densities. Soil samples collected for 30 days post-inoculation were analyzed for viable E. coli by direct plating and/or mini-MPN. Results: Survival of Ec and attO157 populations declined more rapidly in DM compared to PL treatments. By 30 days, at high inoculum densities, Ec counts on PL and DM declined to 4.6 and 2.43 log10 CFU/g, respectively, and attO157 counts declined to 3.83 and 0.46 log10 CFU/g, respectively. No Ec or attO157 were found in control soil. Significance: Manure type, influences the survival of E. coli in soil, with attO157 declining more rapidly than Ec. These findings should be taken into consideration when setting guidelines for fresh produce safety relative to PL and DM application to soil.