Title: 0167 - DNase and Proteinase Trigger Growth of Streptococci Within Oral Biofilms
Thomas Thurnheer (Presenter)
Center of Dental Medicine University of Zurich
Patricia Martin Perez, Center of Dental Medicine University of Zurich
Lamprini Karygianni, Center of Dental Medicine University of Zurich
Objectives: Biofilms consist of microorganisms living in a self-produced matrix of extracellular polymeric substances (EPS) that are mainly polysaccharides, proteins, nucleic acids and lipids. Previous experiments had shown that short expositions of growing biofilms to deoxyribonuclease I (DNase I) and proteinase K did not affect the total CFU in the Zürich supragingival biofilm-model. The aim of this study was to investigate the impact of the presence of DNase I and/or proteinase K during the whole growth phase on in vitro biofilm formation and structure.
Methods: The standard six-species supragingival biofilm employed contained Actinomyces oris, Candida albicans, Fusobacterium nucleatum, Streptococcus mutans, Streptococcus oralis, and Veillonella dispar. Biofilms were grown anaerobically on hydroxyapatite discs in 24-well culture dishes. The growth medium contained 70% saliva and 30% FUM as well as DNase I and proteinase K (0.001mg or 0.002mg, each). After 64 h biofilms were either harvested and quantified by culture analysis or proceeded to staining using anti-DNA antibodies, streptavidin (Cy3), calcofluor, SYPRO Ruby and YoPro-1/Sytox or fluorescent in situ hybridization (FISH) followed by confocal laser scanning microscopy (CLSM).
Results: Neither DNase I nor proteinase K had an impact on total CFU when they were present during the whole growth phase of the biofilms compared to the control without enzymes. However, the combination of DNase I and proteinase K resulted in a significant increase by one or two log10 levels of the CFUs of S. mutans and S. oralis, respectively (p<0.001), whereas C. albicans and V. dispar showed lower CFUs (p<0.001) compared to the control. Overall, a significant increase in total CFU (p<0.001) could be observed.
Conclusions: The reduction of extracellular DNA and proteins by DNase I and proteinase K, respectively, not only affected the biofilm structures, it also favored growth of streptococci probably by reducing nutritional competition.
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: NONE