Genetic relationships of Clostridium bifermentans and Clostridium sordellii analyzed by multilocus enzyme electrophoresis and DNA-DNA hybridization

The genetic relationships of 45 strains belonging to Clostridium bifermentans and C. sordellii were studied by multilocus enzyme electrophoretic analysis. The allelic variations of eight polymorphic enzyme loci, analyzed by a combined polyacrylamide electrophoresis-electrophoretic transfer technique, resolved 42 electrophoretic types (ETs). Clustering analysis of these ETs revealed a two-part distribution on a dendrogram, the two main clusters being separated at a genetic distance of 0.80. The distribution of the strains in the two ET clusters was in agreement with DNA-DNA hybridization experiments (S1 nuclease method) using H-3-labeled DNA of the type strains of both species and DNA from 17 selected other strains. Eight strains whose urease and fermentation profile did not provide a reliable identification could be accurately identified to their DNA group by multilocus enzyme electrophoresis. The genetic diversity of C. bifermentans and C, sordellii was emphasized by the 42 ETs distinguished, and the method allowed the characterization of the clonal relationships of a set of eight isolates originating from the same environmental source. Thus, multilocus enzyme elctrophoresis provides a reliable means for the identification of C. bifermentans and C. sordellii and for the characterization of their genetic diversity.