Genetic heterogeneity of clinical strains of Yersinia enterocolitica traced by ribotyping and relationships between ribotypes, serotypes, and biotypes.

A series of 74 Yersinia enterocolitica clinical strains collected in a Spanish region and 10 reference strains, assigned to nine serotypes and five biotypes, were analyzed by ribotyping procedures. Riboprobing, performed separately with HindIII and BglI and using an rrn operon as the probe, generated 13 and 11 ribotypes (discrimination index [DI] = 0.56 and 0.55), respectively. PCR ribotyping, performed with primers complementary to conserved regions of 16S and 23S rRNA genes, generated 13 ribotypes (DI = 0. 56). A combination of data from the three procedures allowed for further discrimination into 17 combined ribotypes (DI = 0.83). The dendrogram obtained by cluster analysis of data from riboprobing indicated a high heterogeneity of the ribosomal DNA regions of the strains under study (similarities between 10 and 92%), which were grouped into three clusters at a similarity level of 0.32. The major cluster included 10 branches, and 7 of these formed a subcluster (similarity coefficient, >83%) represented by strains of serotype O:3 and biotype 2, 3, or 4. The second cluster included four branches, represented by strains belonging to seven non-O:3 serotypes, biotypes 1A and 2, and two of these branches included pyrazinamidase-positive as well as pyrazinamidase-negative strains. The remaining three branches, represented by O:3-biotype 4 strains, formed a third cluster weakly related to the others. Data from this study showed that Y. enterocolitica O:3 organisms assigned to a prevalent and endemic lineage and non-O:3 organisms assigned to three other less-frequent lineages are circulating and causing human disease in the Spanish region under study.