Bactericidal Action of a Bis-quaternary Ammonium Compound against Vegetative Cells and Spores of Bacillus subtilis

抄録

The bactericidal actions of a novel bis-QAC, 4, 4'-(1, 6-hexamethylenedithio) bis (1-octylpyridinium iodide) (4DTBP-6, 8) against the vegetative cells and the spores of Bacillus subtilis ATCC6633 were investigated. The bactericidal activity (log MBC^-1) did not change in the temperature range of 10-50°C, the pH range of 5.0-9.0 and the contact time over 5min but remarkably depended on the initial cell concentration and the recovery medium. It was found that lecithin contributed to the recovery of the injured bacteria besides inactivating 4DTBP-6, 8 whereas Tween 80 had no effect. Furthermore, 4DTBP-6, 8 exhibited a strong inhibition against the germination and the outgrowth of spores. On the other hand, the kinetics analysis of the bactericidal action revealed that the initial death rate constant (k) for the vegetative cells was much higher than that for the spores. However, the initial death rate constant for the vegetative cells was dependent on both the temperature and pH while this was not the case for the spores. The activation energy (E_a) for the vegetative cells rapidly decreased with the increasing concentration of 4DTBP-6, 8, and the value of E_a (1.97kJ/mol) at the concentration of 9 μM was similar to that (2.10kJ/mol) for the spores at the concentration of 100 μM. The difference the concentration exponent (n) between the vegetative cells and the spores was observed, such as n≅1 for the vegetative cells and n<0.2 for the spores at low temperatures. These results indicate that the spores are much more resistant to 4DTBP-6, 8 than the vegetative cells and suggest that the kinetics of the bactericidal action of 4DTBP-6, 8 against the vegetative cells and the spores are different.