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P1-131 The Effect of Manure Application Method on the Persistence of Eschericha coli in Manure-amended Soils in Southeastern Pennsylvania

Monday, August 4, 2014
Exhibit Hall D (Indiana Convention Center)
Lorna Graham, University of Maryland Eastern Shore, Princess Anne, MD
Daniel Wright, University of Maryland Eastern Shore, Princess Anne, MD
Fawzy Hashem, University of Maryland Eastern Shore, Princess Anne, MD
Corrie Cotton, University of Maryland Eastern Shore, Princess Anne, MD
Alyssa Collins, Pennsylvania State University, Manheim, PA
Kathryn White, U.S. Department of Agriculture-ARS, Beltsville, MD
Richard Stonebraker, U.S. Department of Agriculture-ARS, Beltsville, MD
Manan Sharma, U.S. Department of Agriculture-ARS, Beltsville, MD
Patricia Millner, U.S. Department of Agriculture-ARS, Beltsville, MD
Introduction: Animal manure, used as fertilizer, may introduce enteric pathogens to crops in agricultural fields. FDA proposes a 270-day interval between application of manure and harvest of produce crops.  

Purpose: The persistence of Escherichia coli in manure-amended soils in Pennsylvania and its transfer to growing spinach plants was evaluated.

Methods:  Inoculum containing equal amounts of attenuated, rifampicin-resistant E. coli O157:H7 (attO157) and non-pathogenic E. coli (gEc) was spray-applied at low (LP: 3.9 log CFU/m2) or high (HP: 6.4 log CFU/m2) populations to 2 m2 plots amended with poultry litter (PL), horse manure (HM), or no manure (NM). Manure was either surface-applied or tilled into the soil; spinach was seeded in high PL 7-dpi (days post-inoculation). Surface or core samples of soils were collected to 56-dpi.  E. coli populations (CFU or MPN/g dry weight (gdw)) in soils or from spinach was determined through 56-dpi by direct plating or by mini-MPN.

Results: Populations of gEc declined by 1.1–2.1 and 0.1-2.1 log CFU/gdw in LP and HP unamended plots, respectively, at 56-dpi; however, LP and HP of gEc did not decline in soils amended with PL as in HM-amended soils.  In all manure-amended soils, gEC populations in core samples were >1 log CFU/gdw than surface samples on day 0. In PL plots containing HP, gEc populations were 6.6, 5.0, and 3.1 log CFU/gdw on 7, 28, and 56-dpi, respectively, in core samples.  gEC recovered from spinach plants in HP PL plots were > 6, 3.2, and 0.6 log MPN/gdw at 28-, 46-, and 56-dpi, respectively.  In all plots, LP and HP of attO157declined rapidly by day 3 and none was recovered from spinach planted in PL soils on 7 dpi.          

Significance:  E. coli was transferred to spinach when planted in PL-amended soils containing high populations, and persisted for longer durations in PL compared to HM or NM soils.

Back to: Poster Session - Applied Laboratory Methods, Produce, Low-water Activity, Beverages and Water
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