Salmonella in an Oyster Production and Small Feedlot Environment, Use of Novel Proteins Expressed by an Attenuated Salmonella Vector for the Reduction of Campylobacter Colonization in Broiler Chickens

Abstract

The CDC estimates that 48 million illnesses, 128,000 hospitalizations, and 3,000 deaths annually are attributable to foodborne illnesses, making their impact significant in terms of both human health and economic losses (3). Estimates vary, but it is frequently stated that Campylobacter species affect 2.4 million people annually (28). Among bacterial foodborne pathogens it is second in the US only to Salmonella, which in recent years has consistently been the most frequently reported, most likely to cause hospitalization, and deadliest foodborne bacterial illness in the US (3, 106).In order to reduce the burden of illness caused by these pathogens and improve the safety of our food supply, continued investigation of the epidemiology, transmission and interactions of these organisms with their environments is necessary. Additionally, prevention of colonization within natural reservoirs of these bacteria which contribute to contamination of foods is an important step in the reduction of the burden of foodborne illness. This work examines the relationship of Salmonella to oysters and the aquatic environment in which they are raised, the interactions of Salmonella in a small feedlot environment, and the reduction of colonization of broiler chickens by Campylobacter jejuni through vaccination with recombinant attenuated Salmonella vectors into which novel Campylobacter genes had been cloned. It was found that while Salmonella is still sporadically present on the West Coast of the US, an area where oysters were previously found to be positive for the organism, the strain which predominated in the last study of that area is reduced in prevalence. Additionally, it was found that that strain does not possess special fitness in oysters or the aquatic environments in which they are raised, though Salmonella survives in oysters and water samples longer than a representative coliform. Salmonella is also present in the small feedlot environment sampled, and animal stress appears to play a role in the shedding of the organism in that environment, leading to the potential contamination of beef carcasses during processing. Reduction of colonization by C. jejuni in broilers was achieved in the case of both vaccines, with a maximum reduction of four logs as compared to controls.