Effect of Vancomycin and Glucose on Biofilm Formation by Coagulase-negative Staphylococci: Investigation of Standard Strains and Clinical Strains isolated from Implant-related Infection

[Objective] The objective of this study was to investigate the suppressive effect of antibiotics and presence or absence of glucose on biofilm formation on metal surfaces by coagulase-negative Staphylococci. [Materials and Methods] Bacterial strains included a standard biofilm-forming strain of Staphylococcus epidermidis, nonbiofilm-forming strain of Staphylococcus hominis, and two clinical strains of Staphylococcus epidermidis isolated from implantrelatedinfection (IRI). Vancomycin (VCM) was used as the antibiotic. Trypticase soy broth (TSB) and TSB without dextrose (TSB w/o D) were used as growth media. Each strain was adhered to stainless steel washers and cultured in different growth media with various VCM concentrations for different lengths of time. The degree of biofilm formation was measured as the biofilm coverage rate (BCR). [Results] BCR decreased with increasing VCM concentration and shorter incubation time; however, the degree of suppression varied by strain. BCR was lower for strains cultured in TSB w/o D than for those in TSB. BCR for 8-h incubation group was significantly reduced at lower VCM concentrations in TSB w/o D than in TSB. [Conclusions] Biofilm formation was suppressed in absence of glucose environments, suggesting the importance of controlling blood glucose levels during the perioperative period to prevent IRI