Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/22/2013
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Potential for pathogen transfer from soils amended with untreated animal manure to crops and the frequent occurrence of foodborne illness outbreaks involving Escherichia coli O157:H7 prompted the FDA proposal requiring a 9-month waiting period before harvesting produce from manure-amended fields. Assessment of E. coli survival in fresh produce fields amended with manure will aid evaluation of soil-crop contamination risk and harvest wait periods. This field study investigated survival of inoculated non-pathogenic (gEc) and attenuated O157-E. coli (attO157) in soil manure-amended soils in southeastern Pennsylvania. Multiple strains of gEc and attO157 (rifampicin-resistant, R), cultured separately in poultry litter extract, were combined in equal amounts to produce low and high density inocula (3.9 and 6.4 log CFU/ml, respectively). Field plots were amended with poultry litter (PL), solid (DS) or liquid (DL) dairy manure, horse manure (HM), or no manure (NM) at rates consistent with nutrient management practices, then sprayed with either low or high density inocula. Survival of E. coli populations was determined throughout 0-56 days-post-inoculation (dpi) by enumeration on sorbitol MacConkey agar with rifampicin (SMACR) or by mini-MPN. Low inocula treatment means declined over 0-56 dpi from (2.37 to (-0.08) log CFU(MPN)/g for all manure types, and high inocula treatment means declined from of (3.87 to (0.28) log CFU(MPN)/g. Populations of gEc and attO157 declined relatively slowly in DS and DL regardless of inoculum level; gEC and attO157 populations declined rapidly in plots with no manure. At day 56 all plots were negative for gEC and attO157 except horse and dairy liquids at both high and low inocula. Results show that the type of animal-manure amendment can influence E. coli survival in amended soils. Compared to the relatively rapid decrease of E. coli in non-amended soils, survival time was prolonged for E. coli in manure-amended soils.