Kinetic Analysis of the Bactericidal Action of a Bis-quaternary Ammonium Compound against Escherichia coil

抄録

The bactericidal activity of bis-quaternary ammonium compounds (bis-QACs) such as 4, 4'-(1, 6-hexamethylenedithio) bis (1-octylpyridinium bromide) (4DTBP-6, 8), which possess two quaternary ammonium cations in the molecule, is stronger than that of mono-QAC possessing one ammonium cation in the molecule. It is also reported that the bactericidal action of bis- QACs is less influenced by the molecular hydrophobicity of the drug or environmental conditions such as temperature or pH than that of mono-QAC. In order to clarify the mode of bactericidal action of a bis-QAC, 4DTBP-6, 8, against Escherichia coli, its bactericidal activity was kinetically elucidated compared with that of a mono-QAC, N-octylpyridinium bromide (P- 8). Though there was little difference in the dilution coefficient (n) of 4DTBP-6, 8 and P-8, the minimum effective concentration for the bactericidal action of 4DTBP-6, 8 was different from that of P-8. The rate constant (k) of the bactericidal action of 4DTBP-6, 8 was little influenced by the treatment temperature and the growth temperatures, and the Arrhenius plots of the k values showed a linearity. The apparent activation energy (Ea) for the bactericidal action of 4DTBP-6, 8 was 15.6kJ/mol. On the other hand, the k values of P-8 were extremely influenced by the treatment and growth temperatures, and the Arrhenius plots of the k values gave a broken line. The calculated E_a value was 99.8kJ/mol at a low temperature (10-30°C) and 40.6kJ /mol at a high temperature (30-40°C) Judging from these findings, it is clear that the mechanism of bactericidal action of bis-QAC is different from that of mono-QAC.