title: Synergistic bactericidal effects of a sublethal concentration of didecyldimethylammonium chloride (DDAC) and low concentrations of nonionic surfactants against Staphylococcus aureus.
abstract: DDAC is an effective disinfectant used in the medical and food industries and the environmental field. However, skin irritation in humans occurs at high DDAC concentrations. In this study, we analyzed the combined effect of a low concentration  (0.3 ppm)  of DDAC and low concentrations  (6, 8, and 10 ppm)  of 37 products of nonionic surfactants on the bactericidal activity against S. aureus. No bactericidal activity was found at 0.3 ppm DDAC alone. Results showed that a combination of a low concentration of DDAC  (0.3 ppm)  and some nonionic surfactants tested  (synergistic effect of five products ≥ 2.0)  improved the bactericidal activity of DDAC. Synergistic effects of DDAC and some nonionic surfactants are desirable and were suggested to occur as follows. Test surfactants acted against the cell walls of S. aureus, which allowed DDAC to act easily on the lipid double membrane in the cell wall, thereby increasing the bactericidal activity of DDAC. In the present study, synergistic effects of a low concentration of DDAC and some nonionic surfactants were observed, a phenomenon that may be considerable value in future developments.
authors.affiliation: Research and Development Center, KOBAYASHI Pharmaceutical Co., Ltd., Nara, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Gomi
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Osaki
authors.forename: Miho
authors.initials: M
authors.lastname: Mori
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Sakagami
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002473:Cell Wall / Q000187:drug effects; D004357:Drug Synergism; D006801:Humans; D050296:Microbial Viability / Q000187:drug effects; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000502:physiology; D013501:Surface-Active Agents / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents; C027118:didecyldimethylammonium