Molecular Relatedness of the Prevalent Cryptic Plasmids of Bacteroides Species Isolated in Hungary

The molecular relatedness of plasmids of 44 previously-reported plasmid-bearing Bacteroides strains were examined by Southern hybridization. The identity of 5.5 kb plasmids, which occur most frequently (34.8%) in Hungarian clinical isolates, and 4.2 kb plasmids, the second most prevalent (21.7%) plasmid type were analyzed. Homology with class II and class III plasmids from North American Bacteroides isolates was also investigated. These experiments revealed that the 5.5 kb plasmids are highly homologous and belong in class III, and the 4.2 kb plasmids belong in class IIA. One plasmid belonging to class IIB was observed, and two 4.2 kb plasmids displayed homology to the 5.5 kb group. In geographically closely situated regions, the frequency of occurrence of these plamids is similar, while in distant regions their prevalences differed.