Correlation between zeta-potential of a cell in a new cationic disinfectant solution and minimum inhibitory concentration of the disinfectant.

In the previous paper, we described the synthesis of new quaternary ammonium slats with antimicrobial activity: N-alkyl-N-2-hydroxyethyl-N,N-dimethylammonium butyl phosphate (4) and N-alkyl-N-(2-hydroxy-3-phenoxy)-propyl-N,N-dimethylammonium butyl phosphate (5). In this study, we examined the relationship between the MIC (minimum inhibitory concentration) of these new cationic disinfectants, 4 (six compounds) and 5 (three compounds), and the xi-potential against Escherichia coli in solutions of these compounds. The MIC values of these disinfectants against E. coli were highly correlated with the concentration that induced electric charge inversion (xi-potential=0) of E. coli from negative to positive.