A plethora of natural products emerges as attractive molecules in the struggle against antibiotic resistance. These molecules impose their bioactivities not only alone but also in combinations as well, which further enhances their effects. Berberine is a well-known isoquinoline alkaloid with antibacterial activity. Unfortunately, it is readily extruded, which significantly reduces its efficacy and restricts its potential. Thymol is a monoterpenic phenol that exhibits different biological activities but its major effect is observed only at relatively high concentrations, which raises concern on cytotoxicity. The aim of the study was to potentiate the antibacterial activity of berberine, in a combination treatment with thymol in the opportunistic pathogen Staphylococcus aureus and understand the antibacterial mechanism of the combination treatment. The synergism of berberine and thymol was first established by the checkerboard assay. Then the antibacterial mechanism of the synergistic combination was explored by growth curves, biofilm formation assay, SEM observation, and RNA-Seq based transcriptomic profiling. Checkerboard assay showed that 32 μg mL⁻¹ berberine and 64 μg mL⁻¹ thymol was a synergistic combination, both concentrations below their cytotoxicity limits for many cells. 32 μg mL⁻¹ berberine and 32 μg mL⁻¹ thymol was sufficient to inhibit biofilm formation. SEM images confirmed the morphological changes on the structure of combination treated cells. The major finding of the combination treatment from the transcriptomic analysis was the repression in the expression of virulence factors or genes related to virulence factors. Apart from the particular changes related to the cell envelope, the majority of expressional changes seemed to be similar to berberine-treated cells or to be resulting from general stress conditions. The findings of this work showed that when thymol was used in combination with berberine, it enhanced the antibacterial activity of berberine in a synergistic manner. Furthermore, thymol could be considered as an antivirulence agent, disarming S. aureus cells.

在对抗抗生素抗性的斗争中，大量的天然产物以有吸引力的分子形式出现。这些分子不仅单独施加其生物活性，而且还联合施加其生物活性，这进一步增强了它们的作用。小ber碱是一种众所周知的具有抗菌活性的异喹啉生物碱。不幸的是，它容易被挤出，这大大降低了它的功效并限制了它的潜力。百里酚是一种单萜酚，具有不同的生物活性，但仅在相对较高的浓度下才能观察到其主要作用，这引起了对细胞毒性的关注。该研究的目的是在与机会性病原体金黄色葡萄球菌配合的百里香酚联合治疗中增强小ber碱的抗菌活性。并了解联合治疗的抗菌机理。小by碱和百里香酚的增效作用首先是通过棋盘试验确定的。然后通过生长曲线，生物膜形成测定，SEM观察和基于RNA-Seq的转录组谱分析来探索协同组合的抗菌机制。棋盘检测显示32μgmL ^-1小ber碱和64μgmL ^-1百里酚是一种协同组合，两种浓度均低于许多细胞的细胞毒性极限。32μgmL ^-1小ber碱和32μgmL ^-1百里酚足以抑制生物膜的形成。SEM图像证实了组合处理的细胞的形态变化。从转录组学分析来看，组合治疗的主要发现是抑制了毒力因子或与毒力因子相关的基因的表达。除了与细胞包膜有关的特定变化外，大多数表达变化似乎与经过小ber碱处理的细胞相似，或者是由一般应激条件引起的。这项工作的发现表明，当百里酚与小ber碱联合使用时，它以协同方式增强了小of碱的抗菌活性。此外，百里酚可以被认为是一种抗毒剂，可以解除金黄色葡萄球菌的武装。