Presence of Yersinia enterocolitica in tissues of orally-inoculated pigs and the tonsils and feces of pigs at slaughter

In order to study the early events associated with infection of swine by Ye rsinia enterocolitica, 42 five-week-old crossbred piglets were inoculated p er os with approximately 10(8) Y. enterocolitica O:3. Groups of 5 animals ( and one negative control) were :euthanized 30 min, 3, 6, 12, 24, 48 and 72 h following the infection. Palatine:tonsils, retropharyngeal,and mesenteric lymph nodes, esophagus, duodenum, jejunum, ileum (and Peyer's patches), st omach, liver, spleen and feces (from colon) were collected and analyzed for the presence of Y. enterocolitica by standard bacteriological procedures. Natural infections were also analyzed, as a complementary study, by taking one-gram samples of fecal material :and tonsils from 291 pig carcasses less than 3 h after slaughter and culturing them for Y,enterocolitica using a c old enrichment technique. Within 30 min, Yersinia enterocolitica O:3 was al ready present at most sites. The presence of Y. enterocolitica in the liver of 3 out of 10 animals and also in the spleen of 3 out of 10 piglets, with in the first 3 h postinfection, but no at later times (with one exception), probably indicated a transient bacteremia accompanying he initial stages o f infection. The tonsils were colonized in most animals (13/20) as the bact eria remained present from 12 to 72 h postinfection, while only 4 out of 20 fecal samples were found to be positive over the same period. Up to 10(4) colony-forming units of Y. enterocolitica per gram of tonsil and fecal mate rial were: recovered, Finally, among the 291 animals sampled at the abattoi r, a total of 79 were found positive, 70 of the tonsils sampled were positi ve, and bacteria were recovered in 17 fecal samples, It is therefore Sugges ted that palatine tonsils are the most reliable tissue for the indication o f an infection/colonization by Y. enterocolitica O:3 in swine and that the removal of this tissue during the slaughter process should be considered in order to minimize the possibility of contamination of meat products.