Isolation of Salmonella serotypes from feces of pigs raised in a multiple-site production system

Abstract

Objective To determine the prevalence and serotypes of Salmonella organisms in feces of pigs raised in a modern, multiple-site production system. Design Cross-sectional study of prevalence. Sample Population Swine housed on 7 farms (1 gilt development farm, 2 breeding farms, 1 nursery farm, and 3 finishing farms) that formed a multiple-site production system. Procedure Fecal samples were obtained from 792 pigs (96 to 202/farm) and submitted for bacteriologic culture of Salmonella organisms. Results Salmonellae were isolated from pigs on all 7 farms and from 95 of 792 (12%) fecal samples. Prevalence ranged from 3.4% at the gilt development farm to 18 and 22% at the breeding farms. Serotypes identified were Salmonella derby, S typhimurium var. Copenhagen, S heidelberg, S typhimurium, S mbandaka, S worthington, and S tennessee. No single serotype was not isolated from all the farms of the production system and the most prevalent serotypes at the 3 finishing farms (S typhimurium or S typhimurium var. Copenhagen) were not isolated from the breeding or nursery farms. Clinical Implications Upstream infection (pigs infected before arriving at finishing farms) appears to be an unimportant source of Salmonella infection of finished hogs in multiple-site systems. High prevalence of Salmonella shedding in breeding animals suggests that food products derived from culled breeding livestock may be an important source of foodborne disease. (J Am Vet Med Assoc 1998;212:1925–1929)