D-074. Influence of Polysaccharide Intercellular Adhesin (PIA) on Biofilm Maturation in Staphylococcus epidermidis

M. E. Olson, S. R. Slater, P. M. Dunman, P. D. Fey;
Univ. of Nebraska Med. Ctr., Omaha, NE.

Backgroud: Staphylococcus epidermidis is a significant cause of biomaterial-related infections. Central to the pathogenesis of this bacterium is the ability to adhere to medical devices and the subsequent production of biofilm. Polysaccharide intercellular adhesin (PIA), which is synthesized by enzymes encoded by the icaADBC operon, is a significant component of staphylococcal biofilm. Purpose: The purpose of this study was to determine the effect of the production of polysaccharide intercellular adhesion on biofilm maturation as measured by structural development, metabolic requirements and gene transcription profiling. Methods: S. epidermidis 1457 and an isogenic icaADBC mutant were compared using flow cell methodology. Flow cells allow for continual media sampling, which in turn allowed metabolic requirements to be studied by characterizing amino acid depletion as well as determining which byproducts were produced. GeneChips were used on harvested biofilms from both wild type and icaADBC mutants to determine which subsets of genes were differentially regulated. Additionally, confocal microscopy was employed to observe morphological differences that exist between the wild type and the icaADBC mutant. Conclusions: Significant structural differences were observed in flow cells innoculated with 1457 that were not observed using the icaADBC mutant. These differences where further highlighted via confocal microscopy which showed large variation in adherence and survival patterns of the cells growing in the two different biofilms. Transcriptional profiling revealed that the expression of a wide array of genes is altered as each biofilm matures. Additionally, the expression profiling of both the PIA and non-PIA mediated biofilms were unique, indicating that the presence of PIA is able to indirectly modify gene expression. However, no gross differences were noted regarding metabolic requirements under flow cell conditions. These data suggest that PIA provides significant structural matrix, which creates unique niches that leads to differential gene expression as the biofilm matures.