B-249. Msa Regulates Biofilm Formation in Staphylococcus aureus

A. Schwartz, K. Sambanthamoorthy, M. O. Elasri;
Univ. of Southern Mississippi, Hattiesburg, MS.

Staphylococcus aureus is a Gram-positive bacterium that causes a wide array of community-acquired and nosocomial infections. Infections caused by S. aureus are progressively more difficult to treat owing to the increasing prevalence of antibiotic resistant strains. In addition, S. aureus forms biofilms. Generally, biofilm bacteria show much greater resistance to antibiotics due to changes in gene expression or physiology associated with surface-attached existence. The global regulator, sarA, regulates biofilm formation under both in vitro and in vivo conditions. Recently, we have elucidated the function of a novel locus, msa (modulator of SarA), that is required for the full expression of sarA. In this study, we show that the msa mutant exhibits a significant decrease in biofilm formation under static and flow conditions. Further analysis of the mutant biofilm using GFP and confocal microscopy revealed differences in morphology and thickness when compared to the wild type. Expression studies on biofilm-related genes showed that mutation of msa decreased the expression of arcA, arlS, atl, clfA, and icaR. Collectively, these results indicate that Msa plays a critical role in biofilm formation.