Effects of Powdered Rifampin and Vancomycin Solutions on Biofilm Production of Staphylococcus Aureus on Orthopedic Implants

Abstract Purpose Hardware infections in orthopedic surgery, specifically those involving biofilm producing bacteria, are troublesome and are highly resistant to systemic antibiotics. The purpose of this study was to demonstrate the power of rifampin and vancomycin solutions in inhibiting as well as eliminating in vitro on staphylococcus aureus (S. aureus) biofilm in vitro on stainless-steel implants. Methods A suspension of either S. aureus or a S. aureus containing a plasmid that cods for the green fluorescence protein containing fluorescent protein plasmid was applied to 1x1cm sterile stainless steel orthopedic plating material (coupon). Biofilm development was confirmed by; the quantitative assay (colony forming unit [CFU/coupon]) and visualized using confocal laser scanning microscopy. With this established method of biofilm development, we determined the minimum biofilm inhibitory concentration (MBIC) and the minimum biofilm eradication concertation (MBEC) of Rifampicin and Vancomycin. To determine the MBIC, stainless steel plates were subjected to different concentrations of antibiotic solution and inoculated with overnight cultures of S. aureus. After 24 hours of incubation at 37oC, the biofilms on the untreated and antibiotic-treated coupons were quantified. To determine the MBEC, partial S. aureus biofilms were developed on the coupons and then treated with the different concentrations of each antibiotic for 24 hours. The number of bacteria within the control untreated as well as treated coupons was determined. Results Both rifampin and vancomycin solutions inhibited biofilm production of S. aureus on stainless steel mediums; the MBIC for rifampin and vancomycin were 80ng/mL and 1ug/mL respectively. The MBEC for Rifampicin was similar to the MBIC. However, the MBEC for Vancomycin was 6 mg/ml. Conclusions When applied to orthopedic stainless steel hardware in vitro, solutions of rifampin and vancomycin powder separately or in combination can completely prevent and eliminate biofilm produced by S. aureus. Level of Evidence II;