Staphylococcus aureus-associated infections can be difficult to treat due to multidrug resistance. Thus, infection prevention is critical. Cationic antiseptics, such as chlorhexidine (CHX) and benzalkonium chloride (BKC), are liberally used in health care and community settings to prevent infection. However, increased administration of antiseptics has selected for S. aureus strains that show reduced susceptibilities to cationic antiseptics. This increased resistance has been associated with carriage of specific efflux pumps (QacA, QacC, and NorA). Since prior published studies focused on different strains and on strains carrying only a single efflux gene, the relative importance of these various systems to antiseptic resistance is difficult to ascertain. To overcome this, we engineered a collection of isogenic S. aureus strains that harbored norA, qacA, and qacC, individually or in combination. MIC assays showed that qacA was associated with increased resistance to CHX, cetrimide (CT), and BKC, qacC was associated with resistance to CT and BKC, and norA was necessary for basal-level resistance to the majority of tested antiseptics. When all three pumps were present in a single strain, an additive effect was observed in the MIC for CT. Transcriptional analysis revealed that expression of qacA and norA was significantly induced following exposure to BKC. Alarmingly, in a strain carrying qacA and norA, preexposure to BKC increased CHX tolerance. Overall, our results reveal increased antiseptic resistance in strains carrying multiple efflux pumps and indicate that preexposure to BKC, which is found in numerous daily-use products, can increase CHX tolerance.IMPORTANCE S. aureus remains a significant cause of disease within hospitals and communities. To reduce the burden of S. aureus infections, antiseptics are ubiquitously used in our daily lives. Furthermore, many antiseptic compounds are dual purpose and are found in household products. The increased abundance of antiseptic compounds has selected for S. aureus strains that carry efflux pumps that increase resistance to antiseptic compounds; however, the effect of carrying multiple pumps within S. aureus is unclear. We demonstrated that an isogenic strain carrying multiple efflux pumps had an additive resistance phenotype to cetrimide. Moreover, in a strain carrying qacA and norA, increased chlorhexidine tolerance was observed after the strain was preexposed to subinhibitory concentrations of a different common-use antiseptic. Taken together, our findings demonstrate cooperation between antiseptic resistance efflux pumps and suggest that their protective phenotype may be exacerbated by priming with subinhibitory concentrations of household antiseptics.

中文翻译：

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对金黄色葡萄球菌外排泵介导的抗菌素耐药性的系统分析表明，需要加强抗菌素管理。

由于多重耐药性，金黄色葡萄球菌相关的感染可能难以治疗。因此，预防感染至关重要。诸如氯己定（CHX）和苯扎氯铵（BKC）等阳离子防腐剂在医疗保健和社区环境中广泛使用，以防止感染。然而，已经选择增加对金黄色葡萄球菌菌株的抗菌剂施用，这些菌株对阳离子型抗菌剂的敏感性降低。这种增加的阻力与特定外排泵（QacA，QacC和NorA）的运输有关。由于先前发表的研究集中在不同的菌株和仅携带单个外排基因的菌株上，因此难以确定这些不同系统对防腐剂耐药性的相对重要性。为了克服这个问题，我们设计了一系列带有norA，qacA和qacC单独或组合使用。MIC分析表明，qacA与对CHX，西替米特（CT）和BKC的耐药性增加有关，qacC与对CT和BKC的耐药性有关，并且norA对于大多数测试抗菌剂的基础水平耐药性是必需的。当所有三个泵都存在一个应变时，在MIC中观察到了CT的累加效应。转录分析显示，qacA和norA的表达在暴露于BKC后被显着诱导。令人震惊的是，在携带qacA和norA的菌株中，预先暴露于BKC会增加CHX耐受性。总体而言，我们的结果表明，携带多个外排泵的菌株对细菌的耐药性增强，并且表明在许多日用产品中发现的BKC的预接触可以增加CHX耐受性。金黄色葡萄球菌仍然是医院和社区内疾病的重要原因。为了减轻金黄色葡萄球菌感染的负担，在我们的日常生活中普遍使用了防腐剂。此外，许多抗菌化合物是双重用途的，并且存在于家用产品中。对于金黄色葡萄球菌菌株，已经选择了增加的防腐剂化合物，这些菌株带有外排泵，从而增加了对防腐剂化合物的抵抗力。然而，尚不清楚在金黄色葡萄球菌内携带多个泵的效果。我们证明了携带多个外排泵的等基因菌株对西曲肽具有累加抗性表型。此外，在携带qacA和norA的菌株中，将菌株预先暴露于不同抑菌浓度的另一种常用抗菌剂后，观察到的洗必泰耐受性增强。在一起