Role of Staphylococcus epidermidis Virulence Factors in Adhesion to Intravascular Cannulae

Introduction: The adhesion of bacteria to implanted devices in the human body is a major risk factor that can affect the long-term success of these devices. Staphylococcus epidermidis (S. epidermidis) have few virulence factors which have been identified and reported including autolysin (AtlE), Polysaccharide Intercellular Adhesin (PIA), Fibrinogen Binding Protein (SdrG) and Lipase enzymes (GehC and GehD). These virulence factors play an important role in the pathogenesis of S. epidermidis. Aim: To investigate the role of some of the virulence factors of S. epidermidis in the adhesion to three different types of intravascular cannulae used in hospitals. Materials and Methods: Three different types of most commonly used intravascular cannulae in hospitals were tested in this study. Polytetrafluoroethylene (PTFE), Siliconized Polytetrafluoroethylene (SPTFE) and Vialon cannulae were incubated with different S. epidermidis strains, including the mutant strains that were deficient in a specific virulence factor, each separately. The virulence factors tested with each strain were AltE, PIA, SdrG and Lipase enzymes (GehC and GehD). The number of detached bacteria were determined by plating serial dilutions on agar plates. Experiments were repeated and expressed as means and standard deviations with at least three experiments. Results were computed and analysed using Statistical Package for Social Sciences (SPSS) version20 program. Tabulated values were compared with a student's t-test. Statistical significance was defined as p<0.05. Results: All three types of intravascular cannulae showed significant reduction in adhesion by means of cfu/mL with the mutant strains deficient in adhesion factors when compared to the wild strains. The reduction in the percentages of adhesion of AtlE-strain when compared to wild type strain were 35% for PTFE, 38% for SPTFE and 48% for Vialon cannula. This was statistically significant. PTFE (p-value=0.005), SPTFE (p-value=0.02), and Vialon (p-value=0.001). Likewise, all three types of cannulae showed reduction that was statistically significant except for one mutant strain which was deficient in GehC lipase. However, GehD lipase showed statistically significant reduction in adhesion of bacterial colonies similar to mutant strains for PIA and SdrG indicating a role of these virulence factors in the process of adhesion to biomaterials. Conclusion: The virulence factors of S. epidermidis; AtlE, PIA, SdrG and Lipase GehD, play an important role in the adhesion to intravascular cannulae. Further researches are needed to investigate the involvement of other virulence factors in order to understand and prevent such mechanism.