Quantification of biofilm-associated genes in Staphylococcus epidermidis biofilms: its impact in biofilm formation and 3D structure

摘要

Staphylococcus epidermidisis a common commensal coloniser of the human skin and is currently the mostfrequent cause of biomaterial associated infections. Several studies have attempted to identify thedeterminants that distinguish invasive from commensals S. epidermidisstrains. Its pathogenesis is directlyrelated to its ability to establish multi-layered and highly structured biofilms, resistant to antimicrobialagents. This bacterium expresses several factors that are responsible for the development of the biofilm,including the contribution of specific factors (icaA, aap and bhp genes) in the accumulation phase.Recently, several research groups have been trying to understand the contribution of the genes involvedin biofilm formation. Thus, the main goal was to analyse the gene expression of icaA, aap and bhp andcompare with the formation of the biofilm structure. Two S. epidermidis strains, a clinical and acommensal were characterized at the level of biofilm formation, at different incubation times. Accordingto our results both strains showed an increase of biomass production overtime, revealing the importanceto use screening assays with more than 24 h of incubation. A biofilm structure analysis was also performedto detect the presence of poly-N-acetylglucosamine (PNAG), the major component of S. epidermidisbiofilm matrix. The results revealed a higher production of PNAG only after 48 h for SECOMO034.A1.Finally, the gene expression at two different incubation times was determined, confirming the importanceof the icaA gene in the accumulation stage, explaining the high production of biomass and PNAG. On theother hand, the aap and bhp expression levels raised some questions about their role in the biofilmprocess.