Submitted to: International Association for Food Protection
Publication Type: Abstract only
Publication Acceptance Date: 3/6/2012
Publication Date: 7/22/2012
Citation: Jones, K., Hashem, F., Cotton, C., Roberts, C.L., Sharma, M., Millner, P.D. 2012. Influence of poultry litter and dairy manure on persistence of non-pathogenic E. coli and E. coli O157:H7 applied to fields. International Association for Food Protection. [abstract]. Interpretive Summary:
Technical Abstract: Introduction: Manure amendment of soils used to grow fresh produce can introduce pathogens which may persist and contaminate vulnerable commodities. Edaphic, environmental, and biological factors influence microbial survival differently. Purpose: Determine the influence of manure type applied to field plots on survival of a multi-strain inoculum of non-pathogenic E. coli (Ec) and attenuated E. coli O157:H7 (attO157). Methods: Seventy-nine uniformly-sized field plots grouped by manure type and randomized for low and high-inoculum applications were established with six manure- soil treatments: poultry litter, dairy manure liquids, dairy manure solids plus dairy manure liquids, dairy solids on organic and on conventional soil, and organic soil only. 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 ~5x10^6 CFU/m^2 (low) and 5x10^8 CFU/m^2 (high). Soil samples collected for 14 days post-inoculation were analyzed for viable E. coli by direct plating and/or MPN analysis. Results: On day 0, average populations of both Ec and att0157 recovered from low treatments were 3.4 log CFU/g; whereas populations were 6.1 and 6.0 log CFU/g for Ec and attO157, respectively, in high treatments. After 14 days, Ec counts were 0.9 log CFU/g and 1.4 log CFU/g greater than attO157 counts, for low and high inoculum treatments, respectively. All E. coli survived at higher population densities in poultry litter and dairy manure liquids compared to other manure treatments. Rapid population decreases for attO157 occurred in organic soil and dairy solids treatments. Significance: Manure type can have a substantial influence on E. coli and E. coli O157:H7 survival, and should be taken into account when setting guidelines for fresh produce safety. Non-pathogenic, field-isolated E. coli were more persistent than attO157 in manure-amended soils at 14 days post-inoculation.