Effects of carbon dioxide and sub-lethal levels of antibiotics on adherence of coagulase-negative staphylococci to polystyrene and silicone rubber

Fifty coagulase-negative staphylococci (CNS) strains were investigated for adherence to both silicone rubber and polystyrene using a microtitre tray system. Culture in an atmosphere containing a physiological level of carbon dioxide (5% CO2) profoundly affected adherent growth to both surfaces. Most strains adhered less well in this atmosphere compared to in air alone, with mean reductions in adherence of 84% and 86% to silicone rubber and polystyrene respectively. Occasional strains adhered better in 5% CO2. The effects of antibiotic concentrations equivalent to 1/4 MIC of cefuroxime, ciprofloxacin, vancomycin and teicoplanin on the adherence of 10 CNS strains were also studied. Vancomycin and teicoplanin frequently increased adherence to silicone rubber and polystyrene compared to controls. The effects of antibiotics on adherence were not only strain dependent but also sometimes atmosphere or surface specific. Antibiotic-induced changes in adherence did not appear to correlate with changes in strain protein profiles or surface hydrophobicities.