Die off Rates of Salmonella and Shiga Toxin Producing Escherichia coli in Manure Amended Soil under Natural Climatic Conditions Using Novel Sentinel Chamber System

Abstract

The die-off of Salmonella and Shiga Toxin producing Escherichia coli (STEC) in manure (swine or dairy) amended soil (loam or sandy loam) under field conditions was studied. Pathogen die-off occurred in three phases with an initial rapid decline that then slowed over a period followed by extended persistence at low levels. Survival of both pathogens was favored in the subsurface of loam soil. The decline of STEC was greater in swine manure amended soil compared to dairy manure amended soil, while Salmonella decline was greater in dairy manure amended soil. Fluctuations in moisture and temperature significantly affected the die-off while the season of application (spring vs fall) was less relevant. From the results it was apparent that in most cases pathogen die-off occurred within 120 days although low levels of persistent cells were recovered sometimes beyond this time. The food safety risks from persistent pathogens needs to be further studied.