外排调节基因 oqxR 的突变为肺炎克雷伯氏菌的抗菌药耐药性提供了一个简单的遗传开关。

IF 2.6 4区 生物学 Q3 MICROBIOLOGY
Catherine J Dawson, Amelia Bartczak, Karl A Hassan
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引用次数: 0

摘要

肺炎克雷伯氏菌是全球抗菌药耐药性上升的主要病原体,并被认为是物种间耐药性基因转移的贮藏库。外排泵的上调是一种特别令人担忧的耐药性获得机制,因为在许多情况下,单点突变可同时产生对一系列抗菌素和杀菌剂的耐药性。目前的研究调查了肺炎双球菌染色体中的 oqxR 基因突变,该基因编码 RND 家族外排泵基因的负调控因子 oqxAB。从四株肺炎克氏菌(KP6870155、NTUH-K2044、SGH10和ATCC43816)中筛选出抗性突变体,将其单次暴露于30 µg/mL氯霉素,并选择12个突变体进行全基因组测序,以确定与抗性相关的突变。将氯霉素、四环素或环丙沙星单次接触 MIC 值≥4 X 时产生的耐药突变体重复接种到所有三种抗生素上,以观察对所有化合物的同时交叉耐药性,这表明存在多药耐药表型。研究发现,包括单点突变、缺失和插入在内的多种新型突变破坏了 oqxR,导致对氯霉素、四环素和环丙沙星的耐药性同时显著增加。oqxAB-oqxR 基因座已被调动并分散在许多肠杆菌科物种的质粒上,我们对这些基因座的多样性进行了研究,以评估作用于这些基因的进化压力。对质粒携带的 oqxR-oqxAB 操作子拷贝中的 oqxR 启动子区域进行比较后发现,某些构建体可能会产生截短的 oqxR 转录本,这可能会影响 oqxAB 的调控和表达。在某些情况下,肺炎双球菌中发现了染色体和质粒编码的 oqxAB-oqxR 的共同携带,这意味着存在维持和扩大外排泵的选择压力。鉴于 OqxR 是 oqxAB 的抑制因子,任何影响其表达或功能的突变都会导致多重耐药性。这与抗生素靶点突变形成鲜明对比,后者必须发生在有限的序列空间中才能有效,并且不会影响细胞的适应性。因此,ocxR 可作为一个简单的基因开关,通过 OqxAB 介导的外流促进抗药性的产生。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Mutations in the efflux regulator gene oqxR provide a simple genetic switch for antimicrobial resistance in Klebsiella pneumoniae.

Klebsiella pneumoniae is a pathogen of major concern in the global rise of antimicrobial resistance and has been implicated as a reservoir for the transfer of resistance genes between species. The upregulation of efflux pumps is a particularly concerning mechanism of resistance acquisition as, in many instances, a single point mutation can simultaneously provide resistance to a range of antimicrobials and biocides. The current study investigated mutations in oqxR, which encodes a negative regulator of the RND-family efflux pump genes, oqxAB, natively found in the chromosome of K. pneumoniae. Resistant mutants in four K. pneumoniae strains (KP6870155, NTUH-K2044, SGH10, and ATCC43816) were selected from single exposures to 30 µg/mL chloramphenicol and 12 mutants were selected for whole genome sequencing to identify mutations associated with resistance. Resistant mutants generated by single exposures to chloramphenicol, tetracycline, or ciprofloxacin at ≥4 X MIC were replica plated onto all three antibiotics to observe simultaneous cross-resistance to all compounds, indicative of a multidrug resistance phenotype. A variety of novel mutations, including single point mutations, deletions, and insertions, were found to disrupt oqxR leading to significant and simultaneous increases in resistance to chloramphenicol, tetracycline, and ciprofloxacin. The oqxAB-oqxR locus has been mobilized and dispersed on plasmids in many Enterobacteriaceae species and the diversity of these loci was examined to evaluate the evolutionary pressures acting on these genes. Comparison of the promoter regions of oqxR in plasmid-borne copies of the oqxR-oqxAB operon indicated that some constructs may produce truncated versions of the oqxR transcript, which may impact on oqxAB regulation and expression. In some instances, co-carriage of chromosomal and plasmid encoded oqxAB-oqxR was found in K. pneumoniae, implying that there is selective pressure to maintain and expand the efflux pump. Given that OqxR is a repressor of oqxAB, any mutation affecting its expression or function can lead to multidrug resistance. This is in contrast to antibiotic target site mutations that must occur in limited sequence space to be effective and not impact the fitness of the cell. Therefore, oqxR may act as a simple genetic switch to facilitate resistance via OqxAB mediated efflux.

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来源期刊
Microbiology-Sgm
Microbiology-Sgm 生物-微生物学
CiteScore
4.60
自引率
7.10%
发文量
132
审稿时长
3.0 months
期刊介绍: We publish high-quality original research on bacteria, fungi, protists, archaea, algae, parasites and other microscopic life forms. Topics include but are not limited to: Antimicrobials and antimicrobial resistance Bacteriology and parasitology Biochemistry and biophysics Biofilms and biological systems Biotechnology and bioremediation Cell biology and signalling Chemical biology Cross-disciplinary work Ecology and environmental microbiology Food microbiology Genetics Host–microbe interactions Microbial methods and techniques Microscopy and imaging Omics, including genomics, proteomics and metabolomics Physiology and metabolism Systems biology and synthetic biology The microbiome.
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