Efflux-related resistance to norfloxacin, dyes, and biocides in bloodstream isolates of Staphylococcus aureus
Efflux-related resistance to norfloxacin, dyes, and biocides in bloodstream isolates of Staphylococcus aureus
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DOI：
10.1128/aac.00430-07
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发表时间：
2007-09-01
影响因子：
4.9
通讯作者：
Kaatz, Glenn W.
中科院分区：
文献类型：
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作者：
DeMarco, Carmen E.;Cushing, Laurel A.;Kaatz, Glenn W.
外排是金黄色葡萄球菌的重要耐药机制，但其在菌血症患者中的发生频率尚不清楚。在8个月的时间内收集非重复血流分离株，并测定四种常见外排泵底物（含和不含广谱外排泵抑制剂利血平）的mic （n = 232）。利血平相关的MIC降低4倍被认为是外排的指示。鉴定出四种底物中至少有两种外排的菌株（“外排菌株”[n = 114]）。对于这些菌株，使用实时定量逆转录pcr （qRT-PCR）检测含有或不含利血平的一系列典型底物的mic以及mepA、mdeA、norA、norB、norC和qacA/B的表达。基因表达增加四倍或更多。最常见的外排底物是溴化乙锭和氯己定（分别占外排菌株的100%和96%）。qRT-PCR鉴定出mepA（5株[4.4%]）、mdeA（13株[11.4%]）、norA（26株[22.8%]）、norB（29株[25.4%]）和norC（19株[16.7%]）过表达菌株；23株菌株过度表达两个或多个基因。可能与基因表达增加相关的突变包括mepr失活替代和norA启动子区域插入或缺失。可能与其他分析基因表达增加相关的突变也被观察到。流出菌株占所有研究菌株的49%（114/232株），其中近一半的过表达基因编码MepA、MdeA和/或NorABC（54/114株）。对杀菌剂的敏感性降低可能有助于在环境表面的持久性，氟喹诺酮类药物等药物的外排可能使菌株容易产生高水平的靶向性耐药性。
Efflux is an important resistance mechanism in Staphylococcus aureus, but its frequency in patients with bacteremia is unknown. Nonreplicate bloodstream isolates were collected over an 8-month period, and MICs of four common efflux pump substrates, with and without the broad-spectrum efflux pump inhibitor reserpine, were determined (n = 232). A reserpine-associated fourfold decrease in MIC was considered indicative of efflux. Strains exhibiting efflux of at least two of the four substrates were identified ("effluxing strains" [n = 114]). For these strains, MICs with or without reserpine for an array of typical substrates and the expression of mepA, mdeA, norA, norB, norC, and qacA/B were determined using quantitative real-time reverse transcription-PCR (qRT-PCR). A fourfold or greater increase in gene expression was considered significant. The most commonly effluxed substrates were ethidium bromide and chlorhexidine (100 and 96% of effluxing strains, respectively). qRT-PCR identified strains overexpressing mepA (5 [4.4%]), mdeA (13 [11.4%]), norA (26 [22.8%]), norB (29 [25.4%]), and norC (19 [16.7%]); 23 strains overexpressed two or more genes. Mutations probably associated with increased gene expression included a MepR-inactivating substitution and norA promoter region insertions or deletions. Mutations possibly associated with increased expression of the other analyzed genes were also observed. Effluxing strains comprised 49% of all strains studied (114/232 strains), with nearly half of these overexpressing genes encoding MepA, MdeA, and/or NorABC (54/114 strains). Reduced susceptibility to biocides may contribute to persistence on environmental surfaces, and efflux of drugs such as fluoroquinolones may predispose strains to high-level target-based resistance.