The paper presents the results of bacteriological and molecular investigations on the presence of Y. enterocolitica O:9 in the head, mammary and genital lymph nodes, spleen, liver, and uterus samples originating from 58 cows slaughtered due to the positive results of serological examinations for brucellosis. All samples were cultured for Brucella and Y. enterocolitica and examined in multiplex PCR assay (mPCR), in order to identify the universal 16S rRNA Brucella sp. marker and amplify the perosamine synthetase (per) gene, specific for Y. enterocolitica O:9 only. Out of 58 examined animals, in 23 cases the presence of Y.enterocolitica was demonstrated. Typical Yersinia-suspected colonies were seen after 24-48 h incubation on Cefsulodin-Irgasan- Novobiocin (CIN) Yersinia selective solid medium. The mPCR analysis confirmed the presence of predicted amplicon of 312 bp, typical for Y. enterocolitica O:9 in 20 out of 58 lymph node samples tested and similarly, as in bacteriological examination, other samples were negative. The presence of the 16S rRNA gene of Brucella, generating the amplicon of 905 bp, was not observed in any of the samples tested.
