Relation between serology of meat juice and bacteriology of tonsils and feces for the detection of enteropathogenic Yersinia spp. in pigs at slaughter.

The association between positive serology and culture detection of Yersinia spp. in individual pigs was determined. Pieces of diaphragm from 370 pig carcasses were collected for serological analysis, and tonsils and feces of the same carcass were collected for bacteriological analysis. Detection of anti-Yersinia antibodies in meat juice samples was done using an indirect enzyme-linked immunosorbent assay (ELISA) based on Yops (Yersinia outer proteins). Tonsils and feces were tested for the presence of enteropathogenic Yersinia spp. by direct plating on cefsulodin-irgasan-novobiocin agar plates. Of the 370 meat juice samples, 241 (65.1%) gave a positive serological reaction using a cutoff value of 20%. Enteropathogenic Yersinia spp. (Yersinia enterocolitica serotype O:3 and Yersinia pseudotuberculosis) were found in tonsils of 161 pigs and feces of 30 pigs. Recovery of enteropathogenic Yersinia from the tonsils was highly correlated with positive serotiters, whereas no correlation was found between serology and fecal excretion. Results demonstrated that serology has an acceptable sensitivity, but a relatively low specificity for the rapid detection of enteropathogenic Yersinia spp. in tonsils of pigs at slaughter.