Biofilm-Forming Capacity on Clinically Isolated Streptococcus constellatus from an Odontogenic Subperiosteal Abscess Lesion

S. Treptococcus constellatus, a member of the S. Treptococcus anginosus Group (SAG), and known as part of indigenous oral microbiota, has been described to cause abscesses in various regions of the body, despite this organism appears to be innocuous, in general at its habitat. In this communication, we report a biofilm-forming capacity of a facultative anaerobic gram-positive coccus isolated as a dominant bacterium in an odontogenic subperiosteal abscess lesiony. The clinical isolate designated as strain H39 formed dense meshwork structures around the cells that  are typical for biofilm forming bacteria, and produced viscous materials in its spent culture media. The 16S rRNA gene sequence of strain H39 was 99% homologous to that of S. Treptococcus constellatus ATCC 27823, a type strain for S. Treptococcus constellatus. Phylogenetic analysis using data sets of recN, groEL, tuf and 16S rRNA genes showed a sister relationship between strain H39 and S. Treptococcus constellatus ATCC 27823. Dense meshwork-like structures found on strain H39 were observed on S. Treptococcus constellatus ATCC 27823, but not on S. intermedius ATCC 27335 and S. anginosus ATCC 33397. Biofilm assay using 96-wells polystyrene microtiter plates revealed that S. Treptococcus constellatus strains H39 and ATCC 27823 can form dense biofilm on abiotic materials consistently. S. intermedius ATCC 27335 was able to form biofilm on microtiter plates at a lesser extent to those of S. Treptococcus constellatus strains. S. anginosus ATCC 33397 did not form biofilm on an abitotic material. As conclusions, dense meshwork structures around the cells of S. Treptococcus constellatus, and the capacity of S. Treptococcus constellatus and S. intermedius to form biofilm on abiotic materials as observed in this study might be related to the pathogenicity of these two organism and the tropism of organisms in SAG. As recently suggested, phylogenetic analysis could be a powerful tool for differentiating and identifying clinical isolates belong to SAG.