Correlation between the adsorption tendency of cationic disinfectant onto a synthetic multibilayer and its minimum inhibitory concentration.

Minimum inhibitory concentration (the lowest concentration able to inhibit growth of microorganisms after 48 h contract) could be useful as a measure of bactericidal activity of cationic disinfectants. The relation between the minimum inhibitory concentration (microgram/ml) of cationic disinfectants against gram-negative microorganisms and the adsorption tendency of these compounds onto a lipid bilayer was therefore studied using a quartz crystal microbalance (QCM) coated with synthetic multibilayer film. The adsorbed amounts of these compounds were obtained from the frequency decrease of the QCM in aqueous solutions. The calculated partition coefficients showed a good correlation with the minimum inhibitory concentrations of cationic disinfectants against E. coli and K. pneumoniae, supporting the validity of this method for predicting minimum inhibitory concentration. The results suggest that effective antibacterial agents are only slightly absorbed, and may mostly penetrate through the lipid bilayer.