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There is an increasing need to develop alternative antimicrobials to replace currently used antibiotics. Phytochemicals, such as essential oils, have garnered significant attention in recent years as potential antimicrobials. However, the mechanisms underlying their bactericidal activities are not yet fully understood. In this study, we investigated the bactericidal activity of eugenol oil against Salmonella enterica serovar Typhimurium (S. Typhimurium) to elucidate its mechanism of action. We hypothesized that eugenol exerts its bactericidal effects through the production of reactive oxygen species (ROS), which ultimately leads to cell death. The result of this study demonstrated that the bactericidal activity of eugenol against S. Typhimurium was significantly (p < 0.05) mitigated by thiourea (ROS scavenger) or iron chelator 2,2′-dipyridyl, supporting the hypothesis. This finding contributes to a better understanding of the killing mechanism by eugenol oil. [ABSTRACT FROM AUTHOR]

Studies have shown that the production of reactive oxygen species (ROS) is triggered by bactericidal antibiotics, which contributes significantly to the killing of bacterial cells and increasing mutations in surviving cells. In this study, we hypothesized that exposure of Salmonella to sublethal concentrations of hypochlorite (NaOCl), a commonly used sanitizer in household and food industries increases mutation rates, leading to the development of antibiotic resistance. We found that a sublethal concentration (20 ppm) of NaOCl increased the mutation rates of S. typhimurium 14028s significantly (p < 0.05), which was prevented by the ROS scavenger thiourea, supporting that the increased mutation was due to NaOCl-triggered ROS production. We further found that the exposure of S. typhimurium 14028s to the same sublethal concentration of NaOCl increases resistance to kanamycin among the 3 antibiotics evaluated. The results of this study suggest that when NaOCl applied as a sanitizer fails to kill Salmonella due to diluted local concentrations or presence of organic materials, it can cause an adverse outcome of developing antibiotic resistance of the pathogen. [ABSTRACT FROM AUTHOR]