Evaluation of Reduced Susceptibility to Quaternary Ammonium Compounds and Bisbiguanides in Clinical Isolates and Laboratory-Generated Mutants of Staphylococcus aureus
Evaluation of Reduced Susceptibility to Quaternary Ammonium Compounds and Bisbiguanides in Clinical Isolates and Laboratory-Generated Mutants of Staphylococcus aureus
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DOI：
10.1128/aac.00498-13
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发表时间：
2013-08-01
影响因子：
4.9
通讯作者：
Oggioni, Marco Rinaldo
中科院分区：
文献类型：
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作者：
Furi, Leonardo;Ciusa, Maria Laura;Oggioni, Marco Rinaldo
测定了杀生物剂苯扎氯铵和氯己定对1，602株金黄色葡萄球菌临床分离株的MIC和最低杀菌浓度（MBC）。这两种化合物均表现出单峰MIC和MBC分布（分别为2和4或8 mg/L），没有明显的易感性降低的亚群。为了进一步研究，对所有分离株进行qac基因筛选，其中39株还对诺拉多药耐药（MDR）外排泵的启动子区域进行了测序。qacA、qacB、qacC和qacG基因的存在增加了苯扎氯铵的模式MIC，但没有增加MBC，而只有qacA和qacB增加了氯己定的模式MIC。具有野生型诺拉启动子或诺拉启动子突变的分离株具有相似的杀生物剂MIC分布;值得注意的是，并非所有具有诺拉突变的临床分离株都对氟喹诺酮类耐药。在体外外排突变体可以很容易地选择溴化乙锭和吖啶。需要多次传代以选择具有杀生物剂的突变体，但这些突变体显示出与通过染料选择的突变体相当的表型。所有的突变体显示诺拉的启动子区域的变化，但这些是从临床分离株的这一区域不同。尽管如此，没有一个体外突变体在大蜡螟幼虫的杀伤试验中显示出适应性缺陷。总之，我们的数据提供了一个深入的比较概述外排在S。金黄色葡萄球菌突变体和临床分离株，也表明质粒编码的外排泵不影响杀生物剂的杀菌活性。此外，目前的体外试验似乎不适合预测临床相关的耐药性水平。
The MICs and minimum bactericidal concentrations (MBCs) for the biocides benzalkonium chloride and chlorhexidine were determined against 1,602 clinical isolates of Staphylococcus aureus. Both compounds showed unimodal MIC and MBC distributions (2 and 4 or 8 mg/liter, respectively) with no apparent subpopulation with reduced susceptibility. To investigate further, all isolates were screened for qac genes, and 39 of these also had the promoter region of the NorA multidrug-resistant (MDR) efflux pump sequenced. The presence of qacA, qacB, qacC, and qacG genes increased the mode MIC, but not MBC, to benzalkonium chloride, while only qacA and qacB increased the chlorhexidine mode MIC. Isolates with a wild-type norA promoter or mutations in the norA promoter had similar biocide MIC distributions; notably, not all clinical isolates with norA mutations were resistant to fluoroquinolones. In vitro efflux mutants could be readily selected with ethidium bromide and acriflavine. Multiple passages were necessary to select mutants with biocides, but these mutants showed phenotypes comparable to those of mutants selected by dyes. All mutants showed changes in the promoter region of norA, but these were distinct from this region of the clinical isolates. Still, none of the in vitro mutants displayed fitness defects in a killing assay in Galleria mellonella larvae. In conclusion, our data provide an in-depth comparative overview on efflux in S. aureus mutants and clinical isolates, showing also that plasmid-encoded efflux pumps did not affect bactericidal activity of biocides. In addition, current in vitro tests appear not to be suitable for predicting levels of resistance that are clinically relevant.