Survival of Salmonella in Various Wild Animal Feces That May Contaminate Produce

Abstract

Heightened concerns about wildlife on produce farms and possible introduction of pathogens to the food supply have resulted in required actions following intrusion events. The purpose of this study was to evaluate the survival of Salmonella in feces from cattle and various wild animals (feral pigs, waterfowl, deer, and raccoons) in California, Delaware, Florida, and Ohio. Feces were inoculated with rifampin-resistant Salmonella enterica cocktails that included six serotypes: Typhimurium, Montevideo, Anatum, Javiana, Braenderup, and Newport (10(4) to 10(6) CFU/g). Fecal samples were stored at ambient temperature. Populations were enumerated for up to 1 year (364 days) by spread plating onto tryptic soy agar supplemented with rifampin. When no colonies were detected, samples were enriched. Colonies were banked on various sampling days based on availability of serotyping in each state. During the 364-day storage period, Salmonella populations decreased to <= 2.0 log CFU/g by day 84 in pig, waterfowl, and raccoon feces from all states. Salmonella populations in cattle and deer feces were 3.3 to 6.1 log CFU/g on day 336 or 364; however, in Ohio Salmonella was not detected after 120 days. Salmonella serotypes Anatum, Braenderup, and Javiana were the predominant serotypes throughout the storage period in all animal feces and states. Determination of appropriate risk mitigation strategies following animal intrusions can improve our understanding of pathogen survival in animal feces.