Bactericidal action of 4,4'-(alpha,omega-polymethylenedithio)bis-(1-alkylpyridinium iodide)s

Bactericidal action of novel bis-quaternary ammonium compounds (bis-QACs), 4,4'-(alpha,omega-polymethylenedithio)bis(1-alkylpyridinium iodide)s (4DTBP-m,n) was studied. The bactericidal activity of 4DTBP-m,n in water was not affected by the molecular hydrophobicity unlike general mono-QAC, N-dodecylpyridinium iodide (P-12), while the bacteriostatic activity in the medium was reduced with their hydrophobicity. This result suggested that the hydrophobic materials in the medium interact with 4DTBP-m,n and cover their active moiety. Since the bactericidal activity using the measurement system supplemented with peptone was influenced by the molecular hydrophobicity, this speculation was supported. The plots of the bacteriostatic activities of 4DTBP-m,n against the surface hydrophobicities of various bacteria accord to the straight line as in the case of P-12. The slope of the line of 4DTBP-6,12 was comparatively smaller than that of 4DTBP-6,8, indicating that the compounds having longer alkyl group tend to reduce their activities against the bacteria with hydrophobic cell surface because of their interaction with the hydrophobic materials. The novel bis-QACs have an ability to liberate rapidly and abundantly the turbid materials from cells, that is, a bacterioclastic activity. The bacterioclastic activity of P-n was influenced by the length of alkyl group, while 4DTBP-6,n had almost the same activity regardless of its length. Observation by scanning electron microscope (SEM) revealed that 4DTBP-6,8 fatally damaged Escherichia coli cells, and that the morphological alteration of the cells caused by the bis-QAC was greatly different from that of the usual QAC. Therefore, the effective bacterioclastic action, and excellent bactericidal action is due to the unique dimeric structure of 4DTBP-m,n.