Efficacy of concurrent application of chlorhexidine gluconate and povidone iodine against six nosocomial pathogens

Background: Chlorhexidine gluconate (CHG) and povidone iodine (PI) are rarely used concurrently despite a lack of evidence regarding functional incompatibility of these agents. Methods: CHG and PI, alone and combined, were evaluated against Staphylococcus aureus (methicillin-suseptible S aureus [MSSA] and methicillin-resistant S aureus [MRSA]), Staphylococcus epidermidis (MRSE), Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli using checkerboard microbroth dilution techniques. Minimum bactericidal concentration (MBC) was the concentration (percent wt/vol) that reduced bacterial burden ≥5-log₁₀ colony-forming units/mL at 2 hours when compared with bacterial densities in growth controls. Fractional bactericidal concentration indexes (FBCIs) were calculated to determine CHG and PI compatibility. Additionally, tissue plugs from freshly excised porcine vaginal mucosa were infected with S aureus (MSSA), treated for 2 hours with CHG 3%, PI 5%, or CHG 3% and PI 5% combined and then viable bacteria on the tissue plugs enumerated. Results: In broth, CHG demonstrated dose-dependent bactericidal activity, whereas PI activity was all-or-none. All isolates studied were similarly susceptible to CHG (MBCs: 0.0078% ± 0.0019%, 0.0069% ± 0.0026%, 0.0024% ± 0.0005%, 0.0024% ± 0.0005%, 0.0059% ± 0.0%, and 0.0029% ± 0.0%, respectively). The MBCs of PI were identical (0.625%) for all isolates. Overall, FBCI calculations showed indifference. Treatment of MSSA-infected porcine tissue for 2 hours demonstrated that the CHG-PI combination was superior to either antiseptic alone. Conclusion: FBCIs, determined in broth culture, indicate that combining CHG and PI had no negative impact on antisepsis. Moreover, data from an ex vivo porcine mucosal infection model suggest a potential benefit when combining the 2 antiseptic agents.