Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2005
Publication Date: 11/1/2005
Citation: Bhaduri, S., Wesley, I.V., Bush, E. 2005. Prevalence of pathogenic yersinia enterocolitica strains in pigs in the united states. Applied and Environmental Microbiology. 71(11):7117-7121. Interpretive Summary: Yersinia enterocolitica is a bacterium that is a common cause of food-borne illness in humans. Swine are the only known reservoir for the disease-causing (pathogenic ) Y. enterocolitica, and this bacterium is a serious concern of the pork production and processing industry in the United States. A national study, the National Animal Health Monitoring System (NAHMS) Swine 2000 survey, on the national occurrence of pathogenic Y. enterocolitica in swine in the United States was facilitated by the United States Department of Agriculture (USDA), and the Animal and Plant Health Inspection Service (APHIS) in collaboration with the USDA-Agricultural Research Service (ARS). A specific and sensitive procedure based on the polymerase chain reaction (PCR) was used to determine the prevalence of pathogenic Y. enterocolitica in pig feces. The results of the study showed that swine in the United States harbor pathogenic Y. enterocolitica and are a potential reservoir for strains that cause human illness. Since pork safety begins on the farm, pork producers play a critical role in providing safe pork products for the United States and international consumers. The data collected in the NAHMS Swine 2000 study will provide information to the pork industry on the prevalence and epidemiology of this pathogen, secular trends, and risk factors.
Technical Abstract: Swine are the only known animal from which Yersinia enterocolitica (YE) strains pathogenic to humans are isolated. YE are considered an important bacterial food-borne pathogen impacting the pork production and processing industry in the United States. Since this bacterium is a fecal commensal of swine, the primary goal of this study was to identify the prevalence of pathogenic YE in on-farm pigs using feces as the sample source. This study was conducted as a part of the USDA's National Animal Health Monitoring System Swine 2000 Study. A total of 2,600 swine fecal samples were tested for the presence of pathogenic YE in swine herds. The feces were collected from late finisher pigs from 82 production sites in the 17 pork producing eastern and mid-western United States over a period of 27 weeks (September 2000 to December 2001). One gram from each of the swine fecal samples was suspended in 9 ml of 0.1% peptone in sterile Whirl Pak bags and pummeled in a stomacher. One ml of the suspension was diluted in 9 ml of ITC (Irgasan, ticarcillin, and KClO3) broth, vortexed, and enriched for 48 h at room temperature, then 1 ml of the culture was centrifuged and the pellet was washed with TE buffer. The DNA was extracted and subjected to a fluorogenic 5' nuclease PCR assay for the identification of the chromosomal ail gene. Three hundred forty (12.76%) samples were positive out of the 2,600 tested. Thirty four sites out of 79 (43.03%) contained at least one fecal sample positive for the ail sequence. Twenty one of 45 (46.7%; p=0.0564) samples were positive for ail at one of the sites. Since the presence of YE in feces varied from site to site, there may exist some risk factors that influence its presence on farms. The results from this study will aid in the design of future epidemiological investigations concerning on-farm prevalence and associated factors for pathogenic YE. Additionally, the results support that swine are a reservoir for human infections by YE.