D-070. Identification of Streptococcus sanguinis Genes Required for Biofilm Formation and Examination of their Role in Endocarditis Virulence

X. Ge, T. Kitten, Z. Chen, S. Lee, C. Munro, P. Xu;
Virginia Commonwealth Univ., Richmond, VA.

Background: Streptococcus sanguinis is one of the pioneers in bacterial colonization of teeth, and is one of the abundant species in the oral biofilm. S. sanguinis is also a common viridans streptococcal species implicated in infective endocarditis. The association of biofilm formation and endocarditis virulence remains in doubt. This study is to identify genes required for biofilm formation in S. sanguinis and to determine whether biofilm formation is associated with endocarditis virulence. Methods: Biofilm formation was performed in microtiter plates and quantified by crystal violet staining. The genes required for biofilm formation was examined using a signature-tagged mutagenesis library of S. sanguinis. The endocarditis virulence of biofilm-defective mutants was determined by competitive index assay in a rabbit model. Results: we established a biofilm formation screening system for S. sanguinis. Four genes were identified as contributing to biofilm formation in S. sanguinis that have not previously been associated with biofilm formation in any other bacterium. By examining mutants for attenuation in the rabbit endocarditis model and for reduction in biofilm formation, we found some mutants that were both biofilm-defective and attenuated for endocarditis. However, we also identified mutants with only reduced biofilm formation or with only attenuation in the endocarditis model. Conclusion: These results suggest that biofilm formation is not required for endocarditis virulence in S. sanguinis.