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P3-131 Persistence of Escherichia coli in Manure-amended Soil in Pennsylvania

Wednesday, July 31, 2013
Exhibit Hall (Charlotte Convention Center)
Wilbert Long, University of Maryland Eastern Shore, Princess Anne, MD
June deGraft-Hanson, University of Maryland Eastern Shore, Princess Anne, MD
Natalia Macarisin, University of Maryland Eastern Shore, Princess Anne, MD
David Clark, University of Maryland Eastern Shore, Princess Anne, MD
Alyssa Collins, Pennsylvania State University, Manheim, PA
Corrie Cotton, University of Maryland Eastern Shore, Princess Anne, MD
Fawzy Hashem, University of Maryland Eastern Shore, Princess Anne, MD
Manan Sharma, U.S. Department of Agriculture-ARS, Beltsville, MD
Patricia Millner, U.S. Department of Agriculture-ARS, Beltsville, MD
Introduction: 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 FDA proposed standards 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.

Purpose: This field study investigated survival of inoculated generic E. coli (gEc) and attenuated E. coli O157:H7 (attO157) in manure-amended soils in southeastern Pennsylvania.

Methods: Multiple strains of gEc and attO157 (rifampicin-resistant), 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 (2 m2) 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 1 l of 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 or by mini-MPN.

Results: 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 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. By 56-dpi, all plots, except for HM and DL, were ≤0 MPN/g soil for gEc and attO157.

Significance: 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.

Back to: Poster Session 3 - Applied Laboratory Methods, Novel Laboratory Methods, Produce, Risk Assessment
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