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P1-175 Survival of E. coli in Biological Soil Amendments Applied to Soils in Southeastern Pennsylvania

Sunday, July 26, 2015
Exhibit Hall (Oregon 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 , University of Maryland Eastern Shore , Princess Anne , MD
Manan Sharma , U.S. Department of Agriculture ARS EMFSL , Beltsville , MD
Patricia Millner , U.S. Department of Agriculture ARS EMFSL , Beltsville , MD
Introduction: Farmers utilize raw animal manure to improve soil fertility but may introduce bacterial pathogens to soils used to grow produce crops. The recent FDA “Produce Rule” currently proposes a 9-month interval between the application of manure and harvest of the crop.

Purpose: The study examines persistence of E. coli in manure-amended soils in Pennsylvania.

Methods: Inoculum containing attenuated rifampicin-resistant E. coli O157:H7 (attO157) and non-pathogenic E. coli (gEc) was spray-applied (1,000 ml) at low (3.9  log CFU/ml)  or  high populations (6 log CFU/ml) to the surface of 2 m2 plots containing poultry litter (PL), dairy solids (DS), or no manure treatment (UN). Additional PL, DS and UN plots were tilled after spray application. Surface samples of DS and UN plots and core samples of tilled PL (TPL), DS (TDS), and UN (TUN) plots were collected up to 113 days post-inoculation (dpi).  E. coli populations were determined by enumeration on sorbitol MacConkey agar with rifampicin or by mini-MPN.

Results: High populations of attO157 in DS and UN  declined to < 1 log CFU/gdw (gram dry weight) within 14 d; however, low populations of gEc in DS and UN and of attO157 in DS increased between 0 – 2.5 log CFU/gdw between 0 -14 dpi before consistently declining to the detection limit by 56 dpi. Both low and high populations of gEC in TPL increased by up to 2.5 log CFU/gdw between 0 -14 dpi before declining; other gEc and attO157 populations in TPL, TDS, and TUN, declined to < 1 log CFU/gdw by 56 dpi.  gEc populations declined more slowly in TPL than in TDS or TUN. 

Significance: E. coli populations initially (0 - 14 dpi) fluctuated after the application of manure to soils. Microbial competition, nutrient limitation and/or physiological stress potentially affected E. coli population declines in manure-amended soils.

Back to: Poster Session 1 – Laboratory and Detection Methods, Low-water Activity; Retail and Food Service Safety; Seafood; Communication Outreach and Education; Produce; Food Toxicology; Non-microbial Food Safety; Food Defense; Microbial Food Spoilage
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