Submitted to: Epidemiology and Infection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/10/2014
Publication Date: 5/12/2014
Citation: Tseng, M., Fratamico, P.M., Bagi, L.K., Manzinger, D., Funk, J. 2014. Shiga toxin-producing E. coli (STEC) in swine: prevalence over the finishing period and characterization of the STEC isolates. Epidemiology and Infection. DOI:10.1017/S0950268814001095. Interpretive Summary: Shiga toxin-producing Escherichia coli (STEC) represent a subset of E. coli that produce a toxin that damages human cells known as Shiga toxin (Stx). STEC infections are associated with severe diseases in humans, including hemorrhagic colitis and the potentially fatal hemolytic uremic syndrome. STEC are attributed to more than 170,000 cases of human illness yearly in the U.S. Although cattle are considered important reservoirs for STEC, food products from other animal species, including pork products, have caused sporadic infections and outbreaks. However, little is known on the prevalence and fecal shedding of STEC in clinically healthy swine over time. Thus, a longitudinal study was conducted to fill this gap by investigating fecal shedding of STEC in swine raised on conventional farms during the finishing period. A majority of the fecal samples that were tested were positive for the presence of the Shiga toxin gene, and STEC strains of various types were recovered in at least one sample from over two thirds of the pigs. Furthermore, the virulence (disease causing potential) genes carried by the strains differed, and some of the STEC types recovered have been associated with human illness. These data provide a critical first step to enhance the understanding of the epidemiology of STEC in swine to develop strategies to control STEC shedding on farms and prevent contamination of pork products.
Technical Abstract: This descriptive longitudinal study was conducted to investigate the fecal shedding of Shiga toxin-producing E. coli (STEC) in finishing swine and to characterize the swine STEC isolates that were recovered. Three cohorts of finishing swine (n=50/cohort; total 150 pigs) were included in the longitudinal study. Individual fecal samples were collected every 2 weeks (8 collections/pig) from the beginning (pig age=10 weeks old) to the end (pig age =24 weeks old) of the finishing period. STEC isolates were recovered in at least one sample from 65.3% (98/150) of the pigs, and the frequency distribution of first-time STEC detection during the finishing period resembled a point source outbreak curve. Nineteen O:H serotypes were identified among the STEC isolates. Most STEC isolates (n=148) belonged to serotype O59:H21 and carried the stx2e gene. One O49:H21 STEC isolate carried the eae gene. These data are critical first steps to enhance understanding of swine STEC epidemiology.