Effects of alcohols, povidone-iodine and hydrogen peroxide on biofilms of Staphylococcus epidermidis

Objectives: To test the effects of several biocides [N-propanol, a commercially available propanol/ ethanol/chlorhexidine mixture, polyvinylpyrolidone (povidone-iodine) and hydrogen peroxide] on established biofilms of Staphylococcus epidermidis isolated from patients with cardiac implant infections and catheter-related bacteraemia. Methods: Biofilms were grown in microtitre plates for 24 h, dyed and stained with Crystal Violet. The mean optical density (OD) and the OD ratio (ODr= OD of the treated blofilm/OD of the untreated biofilm) were used for quantification. Biofilms were incubated with 60% (v/v) N-propanol, the mixture of propanol/ethanol/chlorhexidine, hydrogen peroxide at three concentrations (0.5%, 3% and 5%, v/v) and povidone-iodine for 1, 5, 15, 30 and 60 min. Unstained biofilms were sonicated and plated on Columbia agar for time-kill curves. S. epidermidis skin isolates from healthy volunteers were used as controls. Results: Biofilm ODs of the clinical S. epidermidis isolates and the isolates from the healthy volunteers were significantly different (1.17 +/- 0.512 versus 0.559 +/- 0.095, respectively; mean +/- SD) (P < 0.01). No viable S. epidermidis was detected in biofilms treated with the alcohols, N-propanol or the propanol/ ethanol/chlorhexidine mixture. Incubation with povidone-iodine and hydrogen peroxide 3% and 5% led to a log reduction of the viable cells of >5 after incubation for 5 min, however, Up to 103 viable cells were detected in four isolates after 30 min of incubation with povidone-iodine. Conclusions: S. epidermidis obtained from infected implants forms thicker biofilms than that of healthy volunteers. Hydrogen peroxide, at a concentration of 3% and 5%, and alcohols rapidly eradicate S. epidermidis biofilms, whereas povidone-iodine is less effective.