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

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 multiplesite production system. PROCEDURE: Fecal samples were obtained from 792 pigs (96 to 202/farm) and submitted for bacteriolgic 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.