Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland.
Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland.
Microbiologyopen. 2020 Apr;9(4):e1005. doi: 10.1002/mbo3.1005. Epub 2020 Feb 13.
Staphylococcus aureus carries a collection of mobile genetic elements that often harbor virulence and antimicrobial resistance genes. Since the introduction of antibiotics, plasmids have become a major genetic element responsible for the distribution of antimicrobial resistance. Under antimicrobial selection, resistance plasmids are maintained within bacterial populations as a means to ensure survival. However, in the absence of selection, large plasmids can be lost due to the fitness costs associated with harboring these genetic elements. pC02 is a previously identified multidrug resistance, conjugative plasmid that is found in S. aureus. In addition to antibiotic resistance, pC02 also carries genes known to be associated with antiseptic resistance. Among these, we previously characterized the contribution of qacA to pC02 mediated reduced chlorhexidine susceptibility. Herein, we demonstrate that pC02 also mediates triclosan resistance, likely due to the presence of fabI, a known triclosan resistance gene. Moreover, we demonstrate that conjugative transfer of pC02 increases triclosan resistance in recipient cells. Competition assays demonstrated a fitness cost associated with carriage of the large pC02 plasmid. However, subinhibitory concentrations of either chlorhexidine or triclosan abrogated this fitness cost. Given the widespread use of these antiseptics, both of which accumulate in wastewater and other environmental reservoirs, indiscriminate use of antiseptics likely imposes a constant selective pressure that promotes maintenance of antimicrobial resistance factors within S. aureus.
金黄色葡萄球菌携带一系列移动遗传元件，这些元件通常含有毒力和抗微生物药物耐药性基因。自抗生素问世以来，质粒已成为导致抗微生物药物耐药性传播的主要遗传元件。在抗微生物药物选择压力下，耐药质粒作为确保存活的一种手段在细菌群体中得以维持。然而，在没有选择压力的情况下，由于携带这些遗传元件相关的适应性成本，大质粒可能会丢失。pC02 是先前鉴定的一种多药耐药性、可接合的质粒，存在于金黄色葡萄球菌中。除了抗生素耐药性外，pC02 还携带已知与防腐剂耐药性相关的基因。在这些基因中，我们之前已经描述了 qacA 对 pC02 介导的降低氯己定敏感性的贡献。在此，我们证明 pC02 还介导三氯生耐药性，这可能是由于存在 fabI，这是一种已知的三氯生耐药基因。此外，我们证明了 pC02 的接合转移会增加受体细胞中的三氯生耐药性。竞争实验表明，携带大质粒 pC02 存在适应性成本。然而，氯己定或三氯生的亚抑菌浓度消除了这种适应性成本。鉴于这些防腐剂的广泛使用，它们都在废水和其他环境储层中积累，对防腐剂的不加区分的使用可能会对金黄色葡萄球菌中的抗微生物药物耐药性因素的维持施加持续的选择性压力。
