Prevalence, Serotype, Virulence Characteristics, Clonality, and Antibiotic Susceptibility of Pathogenic Yersinia enterocolitica from Swine Feces

Abstract

A national study was conducted for the isolation of pathogenic Yersinia enterocolitica from pig feces in the United States as part of the National Animal Health Monitoring System Swine 2000 study. A total of 2,793 fecal samples collected from swine operations from September 2000 to March 2001 from 77 production sites in the 15 eastern and mid-western swine-producing states were tested for the presence of pathogenic Y. enterocolitica. Forty-one of 77 premises (53.25%) harbored at least one fecal sample positive for the ail sequence. Of 2,793 fecal samples tested, 106 (3.80%) ail-positive strains of Y. enterocolitica were isolated by the culture method. These 106 ail-positive isolates originated from 7 of the 15 participating states. The predominant serotype O:3 (n = 79 of 106) was distributed in five states (n = 5 of 7). Serotype O:5 (n = 27 of 106) was also found in five states (n = 5 of 7). All isolates contained the virulence plasmid (pYV) and expressed virulence-associated phenotypic characteristics. The presence of pYV, expression of pYV-associated phenotypes, and serotype were correlated with genotype, expression of the YopE protein, and antibiotic susceptibility. Pulsed-field gel electrophoresis using the enzyme XbaI showed that O:3 and O:5 isolates were highly clonal within a serotype regardless of geographic origin. All isolates tested were susceptible to 13 of the 16 tested antimicrobials; resistance was noted to ampicillin, cephalothin, and tetracycline. The presence of the ail gene, serotypes, and pYV-encoded virulence determinants indicates that swine are a reservoir for Y. enterocolitica that are potential human pathogens. The results from this study will aid in the design of epidemiological investigations elucidating on-farm risk factors associated with pathogenic Y. enterocolitica.