Role of Staphylococcus aureus protein A in adherence to silastic catheters.

BACKGROUND: Communities of bacteria, termed biofilms, frequently develop on central venous catheters, and bacterial contamination of central venous catheters is the most common cause of nosocomial bloodstream infections. Little is known about the initial events in bacterial adherence to the catheter surface, and experiments were designed to clarify the role of staphylococcal protein A, serum, and immunoglobulin in adherence of Staphylococcus aureus to silastic catheters. We hypothesized that S. aureus protein A in the presence of serum and immunoglobulin would alter S. aureus adherence to silastic catheters. MATERIALS AND METHODS: Three strains of S. aureus with varying expression of staphylococcal protein A were incubated 15 min at room temperature with silastic catheters, and bacterial adherence to the catheter surface was quantified. In addition, the effects of serum, albumin, and purified IgG on bacterial adherence were assessed. RESULTS: Both serum and albumin had an inhibitory effect on S. aureus adherence to the catheter surface, and protein A expression did not appreciably modulate these effects. Purified serum IgG also inhibited S. aureus adherence, with IgG having a greater inhibitory effect on the adherence of an S. aureus strain deficient in protein A compared with an S. aureus strain expressing high levels of protein A. CONCLUSION: S. aureus adherence to silastic catheters was inhibited by whole serum, albumin, and purified IgG. Expression of staphylococcal protein A interfered with IgG mediated inhibition of bacterial binding to the catheter surface. Protein A altered S. aureus adherence to silastic catheters in the presence of immunoglobulin, but not in the presence of serum or albumin.

Selected factors affecting Staphylococcus aureus within silastic catheters.

BACKGROUND: Catheter-related infections are frequent complications in hospitalized patients, and Staphylococcus aureus is a frequent etiologic agent. Little is known about factors that contribute to the growth and viability of S. aureus within contaminated catheters. MATERIALS AND METHODS: In vitro experiments assessed the ability of S. aureus to adhere to silastic catheter tubing. The effects of heparin, serum, and calcium on initial bacterial adherence were also assessed. Additional experiments quantified the effect of ethanol locking on S. aureus viability within catheter-associated biofilms produced after 48 to 72 h incubation of S. aureus with catheters under conditions of nutrient flow. Scanning electron microscopy visualized the effect of ethanol locking on the morphology of bacterial vegetations adherent to the catheter wall. RESULTS: S. aureus readily adhered (in a dose dependent manner) to silastic catheters incubated with bacteria for 15 min, and adherence was not affected by calcium or heparin (even though heparin adhered to the silastic tubing and S. aureus is known to express heparin-binding proteins). S. aureus adherence was inhibited by serum but not albumin. Ethanol locking (5 min to 24 h) of catheters containing mature 48 to 72 h S. aureus biofilms resulted in no detectable bacterial viability, although scanning electron microscopy revealed similar bacterial vegetations adherent to control and ethanol-treated catheters. CONCLUSION: S. aureus adherence to silastic catheters was inhibited by serum, but the active inhibitory component was not albumin. Ethanol locking efficiently sterilized S. aureus contaminated catheters, although nonviable bacterial vegetations remained on the ethanol-treated catheters.