The enterococcal surface protein, Esp, is involved in Enterococcus faecalis biofilm formation

The enterococcal surface protein, Esp, is a high-molecular-weight surface p rotein of unknown function whose frequency is significantly increased among infection-derived Enterococcus faecalis isolates. In this work, a global s tructural similarity was found between Bap, a biofilm-associated protein of Staphylococcus aureus, and Esp. Analysis of the relationship between the p resence of the Esp-encoding gene (esp) and the biofilm formation capacity i n E. faecalis demonstrated that the presence of the esp gene is highly asso ciated (P < 0.0001) with the capacity of E. faecalis to form a biofilm on a polystyrene surface, since 93.5% of the E. faecalis esp-positive isolates were capable of forming a biofilm. Moreover, none of the E. faecalis esp-de ficient isolates were biofilm producers. Depending on the E. faecalis isola te, insertional mutagenesis of esp caused either a complete loss of the bio film formation phenotype or no apparent phenotypic defect. Complementation studies revealed that Esp expression in an E. faecalis esp-deficient strain promoted primary attachment and biofilm formation on polystyrene and polyv inyl chloride plastic from urine collection bags. Together, these results d emonstrate that (i) biofilm formation capacity is widespread among clinical E. faecalis isolates, (ii) the biofilm formation capacity is restricted to the E. faecalis strains harboring esp, and (iii) Esp promotes primary atta chment and biofilm formation of E. faecalis on abiotic surfaces.