Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/22/2013
Publication Date: N/A
Citation: N/A Interpretive Summary:
Technical Abstract: Introduction: Recently released U.S. FDA standards state that untreated biological soil amendments must be applied to soil 9 months before produce crop harvest to reduce pathogen contamination risk on produce. Manure and soil type may impact survival of bacterial pathogens. Purpose: Determine survival of three non-pathogenic E. coli (gEc) and two attenuated E. coli O157:H7 (attEc) strains in various untreated animal manures as influenced by surface application to soils. Methods: E. coli strains cultured separately in poultry litter extract, were composited to produce a high (5.8 log CFU/ml), and a low (3.8 log CFU/ml) population inocula, which was surface-sprayed onto conventional and organic field plots (2m sq) amended with poultry litter (PL), solid (DS) or liquid (DL) dairy manure, horse manure (HM), or no manure (NM). Survival was determined over 56 days post inoculation (dpi) by enumeration of colonies on sorbitol MacConkey agar with rifampicin (SMACR), or by MPN procedure. Results: Low and high inocula of all isolates decreased ca. 2.5 and 4.5 logCFU(MPN)/g respectively in conventional soils by 56-dpi. In organic soils, high inocula for all isolates decreased from ca. 4.5 logCFU/g to non-countable, whereas low inocula gEc declined from ca. 2.9 logCFU/g to zero and attEc decreased from 2.6 CFU/g to zero. Populations of both gEc and attEc in low and high inocula declined more slowly in PL, DS, and HM compared to populations in DL and NM. Interestingly, both low and high inocula from all manure treatments were unable to be quantitatively recovered on day 28. Significance: Results indicate that manure type influences the survival of both generic and E. coli O157:H7 strains in manure-amended soils. Environmental factors (e.g., soil moisture fluctuations) and inocula conditioning also may influence the rate of bacterial population decline in manure-amended soils and should be examined more closely.