DISCRIMINATORY POWER AND APPLICATION OF RIBOTYPING OF YERSINIA-ENTEROCOLITICA-0 3 IN AN EPIDEMIOLOGIC-STUDY/

Ribotyping performed with five restriction endonucleases was used in a n attempt to subtype Yersinia enterocolitica serotype O:3 and also as a tool for clonal analysis, DNA from organisms under study (48 isolate s from diarrheic human feces, 24 from food, and 5 reference strains) w as tested by Southern hybridization using a DNA probe carrying an rRNA operon from Escherichia coli. Strains were grouped into seven ribotyp es by the HindIII restriction endonuclease, into five ribotypes by Nci l, BglI, and SalI; and into two ribotypes by EcoRI, resulting in a dis crimination index (DI) of 0.37, 0.17, 0.43, 0.13, and 0.03 for the fiv e endonucleases. By combining the results obtained with two or more re striction endonucleases, a further discrimination was registered, the most efficient combination (in terms of discriminatory power vs, cost in work, time, and money) for routine typing being HindIII-BglI (9 typ es, DI=0.58). In the clonal analysis, results obtained with the five r estriction endonucleases allowed us to define 11 groupings or clonal l ines, which showed a remarkable degree of genetic heterogeneity (genet ic distance coefficients between 0.03 and 0.73) and were grouped into two major clusters, One cluster included 93% of the strains and eight lines. At least two of the most frequent lines can be considered endem ic in Asturias, Spain, because organisms belonging to these lines have been circulating and causing human yersiniosis in recent years and ha ve also been isolated from commercial raw meat products. Two Ncil ribo types from the series under study (92.2% of strains included in the pr evalent cluster) were similar but not identical to ribotypes of O:3 or ganisms from other geographic areas described in the literature, indic ating that the genetic structure of prevalent human pathogens of this serotype is basically clonal.