It is well known that a few strains of Prevotella intermedia have three classes of native plasmids. Previously, the sequence alignment, eight putative open reading frames, and two gene functions were determined for one of the three plasmids, pYHBi 1, which has a molecular size of 5.0-kb. In this study, using electrophoresis and pYHBi 1 targeted PCR, we investigated the presence of native plasmids in 8 extracellular polysaccharide (EPS) producing Prevotella intermedia clinical strains and in the ATCC type strain. We found that our stock strains lacked any type of native plasmid. However, we identified some biofilm-forming clinical isolates that did not have native plasmid. The results suggest there was no correlation between EPS producibility and native plasmids.
