Background

Colistin belongs to the last-resort antibiotics. The discovery of plasmid-bound colistin resistance mediated by the mcr-gene(s) is of great concern because, given its biological potential, there is a risk of its rapid spread.

Objectives

To discuss the current literature on the methods for the screening for mcr-mediated resistance to colistin.

Sources

Literature was drawn from a search of PubMed from 1 January 2016 to 26 April 2021.

Content

The selective culture-based or culture-independent approach can be used for the screening of mcr-mediated resistance to colistin in clinical samples. Rapid Polymyxin NP, Colistin Drop or Colistin Agar Spot tests are applicable for the selection of isolates with a suspected resistance to colistin that has to be confirmed by broth microdilution. The mcr-mediated resistance to colistin can be confirmed by the detection of the causal gene(s) or by phenotype using EDTA-colistin broth disc elution; production of the MCR-1 enzyme can be confirmed with lateral flow immunoassay, using matrix-assisted laser desorption/ionization time-of flight or liquid chromatography-based mass spectrometry. Whole-genome sequencing (WGS) is the ultimate typing method. When a WGS platform is not available at a healthcare facility, a WGS-outsourced service, in combination with freely available bioinformatics tools, allows for the characterization of the mcr-gene(s) carrying isolates.

Implications

mcr-mediated colistin resistance should be monitored through active targeted screening. The broth microdilution method is required for colistin susceptibility testing but as only a selected number of clinical isolates are tested, colistin resistance, including mcr-mediated, may remain undetected. In mcr-1-positive Escherichia coli isolates, the MIC to colistin can range from 2 to 8 mg/L, so it is proposed that Enterobacterales with a colistin MIC of 2 mg/L should also be included in the mcr-mediated colistin resistance screening and those with a confirmed mcr-genotype and/or MCR-phenotype should be considered to be colistin-resistant.

中文翻译：

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如何：筛查 mcr 介导的粘菌素耐药性

背景

粘菌素属于最后的抗生素。由mcr-基因介导的质粒结合粘菌素抗性的发现引起了极大的关注，因为鉴于其生物学潜力，它存在快速传播的风险。

目标

讨论目前关于筛选mcr介导的粘菌素耐药性方法的文献。

来源

文献来自 2016 年 1 月 1 日至 2021 年 4 月 26 日期间对 PubMed 的搜索。

内容

选择性的基于培养或不依赖培养的方法可用于筛选临床样本中mcr介导的对粘菌素的耐药性。快速多粘菌素 NP、粘菌素滴剂或粘菌素琼脂点试验适用于选择对粘菌素有疑似耐药性且必须通过肉汤微量稀释确认的分离株。该MCR- 介导的对粘菌素的抗性可以通过检测致病基因或通过使用 EDTA-粘菌素肉汤圆盘洗脱的表型来确认；MCR-1 酶的产生可以通过侧向流动免疫测定、使用基质辅助激光解吸/电离飞行时间或基于液相色谱的质谱法来确认。全基因组测序（WGS）是最终的分型方法。当医疗机构没有 WGS 平台时，WGS 外包服务与免费提供的生物信息学工具相结合，可以对携带mcr基因的分离株进行表征。

影响

应通过主动靶向筛查监测mcr介导的粘菌素耐药性。粘菌素敏感性测试需要肉汤微量稀释法，但由于仅测试了选定数量的临床分离株，包括mcr介导的粘菌素耐药性可能仍未检测到。在mcr-1阳性的大肠杆菌分离株中，对粘菌素的MIC范围为2～8mg/L，因此建议粘菌素MIC为2mg/L的肠杆菌也应包括在mcr介导的粘菌素耐药中。筛查和确认具有mcr基因型和/或 MCR 表型的患者应被视为对粘菌素耐药。