The role of extracellular polymers on Staphylococcus epidermidis biofilm biomass and metabolic activity.

Staphylococcus epidermidis is now well established as a major nosocomial pathogen, associated with indwelling medical devices. Its major virulence factor is related with the ability to adhere to indwelling medical devices and form biofilms. In this study, the biofilm matrix of four S. epidermidis clinical isolates was extracted and the polysaccharides and proteins content was quantified. The results were correlated with the total biofilm biomass (determined by crystal violet assay) and cellular metabolic activity (evaluated with XTT reduction assay). According to the results, the exopolymers studied play an important role not only on structure and biofilm biomass but also on cellular activity. Thus, the strain forming biofilms with the highest level of polysaccharides (S. epidermidis 1457) also formed thicker biofilms but with the lowest metabolic activity. The protein concentration also varied among strains, with the biofilm matrix of S. epidermidis 9142 presenting a higher concentration of proteins comparing to the remaining strains. This fact indicates the different levels of importance that matrix proteins can hold on biofilm composition among strains albeit overall, it is suggested that extracellular protein production it is not a determinative factor for biofilm total biomass.