Molecular characterization of Haemophilus ducreyi by ribosomal DNA fingerprinting

Intraspecies genotypic heterogeneity among Haemophilus ducreyi isolates was examined by using genomic fingerprints with rRNA from Escherichia coli as a probe. DNA from 44 isolates of H. ducreyi was digested by restriction endonuclease HincII or HindIII, separated by agarose gel electrophoresis, transferred to nylon membranes, and hybridized with 32P-labeled 16S and 23S rRNA. HincII digests yielded four hybridization patterns (ribotypes), whereas HindIII digests yielded eight ribotypes. Four HincII and five HindIII ribotypes were observed among 14 H. ducreyi isolates collected within a period of 1 month in Kenya, where chancroid is endemic. In contrast, one HincII and two HindIII ribotypes were observed among 28 isolates collected during the Orange County, Calif., chancroid epidemic that occurred in 1981 and 1982. The plasmid content, in conjunction with ribotyping, provided additional differentiation among some isolates of H. ducreyi. This study demonstrates that ribotyping of H. ducreyi may be used to study the epidemiology of chancroid.