Effects of chlorhexidine gluconate and chlorous acid-chlorine dioxide on equine fibroblasts and Staphylococcus aureus.

Equine fibroblasts and Staphylococcus aureus were exposed for 30 minutes to six dilutions of chlorhexidine gluconate, a chlorous acid-chlorine dioxide irrigation solution, a chlorous acid-chlorine dioxide disinfectant, and phosphate buffered saline controls. Cell viability was determined by trypsinizing the cells, staining them with trypan blue, and counting cells that did not take the stain. All fibroblasts were killed when exposed to 1.0% and 0.5% chlorhexidine. The survival rate of fibroblasts increased linearly with decreasing concentrations of chlorhexidine gluconate, with a peak survival of 50% at 0.005% chlorhexidine. The chlorous acid-chlorine dioxide irrigation solution was the least toxic to fibroblasts, with survival rates equivalent to those of controls. The chlorous acid-chlorine dioxide disinfectant was 100% cytotoxic even when diluted 1:1 with phosphate buffered saline. S. aureus growth was inhibited by 1.0% and 0.5% chlorhexidine gluconate; concentrations of 0.05%, 0.01%, and 0.005% did not differ from sterile water controls. The chlorous acid-chlorine dioxide irrigation solution did not inhibit growth of S. aureus in brain-heart infusion broth. The chlorous acid-chlorine dioxide disinfectant inhibited growth of S. aureus.