The prevalence and concentration of Salmonella enterica in poultry litter in the southern United States

Poultry litter is applied to crop production land in the southern United States as a waste management strategy as it is a nitrogen-rich fertilizer and plentiful throughout the region. While litter is a known reservoir for human enteric pathogens including Salmonella enterica, little is known regarding pathogen prevalence, concentration, and common serotypes within the material. Litter from thirteen farms across four southern states was examined for Salmonella. Samples (n = 490) from six of the thirteen (46.2%) farms tested positive. Thirty-three samples out of 490 (6.7%) were Salmonella positive. Salmonella was ca. 95% less likely to be collected from stacked litter piles than from the poultry house floor or pasture, and every day increase in litter age reduced the likelihood of recovering Salmonella by 5.1%. When present, concentrations of Salmonella in contaminated poultry litter were variable, ranging from <0.45 to >280,000 MPN/g. The most prevalent serotypes found were Kentucky (45.5%), Kiambu (18.2%), and Michigan (12.1%). Salmonella Kentucky also had the greatest distribution and was found on 4 of the 6 (66.7%) positive farms. Results from this survey demonstrated that Salmonella prevalence and concentration in poultry litter is highly variable, and good agricultural practices are critical to safely use poultry litter as a soil amendment on fresh produce fields.