Limited effectiveness of chlorhexidine based hand disinfectants against methicillin-resistant Staphylococcus aureus (MRSA)

Hand disinfectants containing chlorhexidine are thought to be less bactericidal against methicillin-resistant Staphylococcus aureus (MRSA) than methicillin-susceptible Staphylococcus aureus (MSSA). We report an in vitro comparison between three distinct MRSA strains and three MSSA strains. The bactericidal efficacy of chlorhexidine digluconate, 'Hibiscrub' and 'Hibisol' against Staphylococcus aureus was determined in a quantitative suspension test. Logarithmic reduction factors (RF) were calculated for each of six parallel experiments. Chlorhexidine digluconate and 'Hibisol' showed RF>5 at most concentrations and reaction times but 'Hibiscrub' did not. MRSA was found to be significantly less susceptible than MSSA, to chlorhexidine digluconate, 'Hibiscrub' and 'Hibisol' (P<0.05; two-tailed t-test for independent samples). 'Hibisol' was significantly more effective against MRSA than 'Hibiscrub' (P<0.05). Hand disinfectants containing both alcohol and chlorhexidine (e.g., 'Hibisol') are more effective against MRSA than scrubs based only on chlorhexidine ('Hibiscrub') and should be used in clinical practice.