Increased biofilm formation by clinical isolates on surfaces covered with plasma proteins.

Biofilm formation is a major virulence factor associated with infections. However, the influence of plasma proteins on biofilm formation of clinical isolates remains unclear. We hypothesized that coating surfaces with plasma proteins might induce biofilm formation by of different clonal lineages.. To evaluate biofilm production by clinical isolates of different clonal lineages isolated in Rio de Janeiro hospitals and investigated the presence of biofilm-associated genes. This study assessed biofilm production of 60 isolates in polystyrene microtitre plates with and without fibrinogen or fibronectin. The biochemical composition of the biofilm matrices was determined and the biofilm formation on fibrinogen-coated surfaces was also evaluated by confocal laser scanning microscopy. The presence of biofilm-related genes was detected by PCR, and the typing and functionality of was also evaluated. Most of the isolates (45 %) were weak biofilm producers or non-producers. However, most of them presented a significant increase in biofilm production on plates covered with plasma proteins. There was no significant difference in biofilm formation between methicillin-resistant and -susceptible isolates, or between different clonal lineages, except for ST30-IV (weak producers) and ST239-III (strong producers). The gene was associated with higher biofilm production. An increase in biofilm production in the presence of plasma proteins highlights the importance of investigating biofilm formation by clinical isolates under different conditions since this virulence factor contributes to persistent infections and increased resistance to antimicrobials.