Downregulation of an NfsA-like nitroreductase causes metronidazole resistance in Gardnerella vaginalis

IF 5 2区医学 Q1 INFECTIOUS DISEASES

International Journal of Antimicrobial Agents Pub Date : 2026-02-01 Epub Date: 2025-12-01 DOI:10.1016/j.ijantimicag.2025.107681

Ana Paunkov , Anna-Lena Mayr , Vera Oberbauer , Timo Schwebs , Lorenzo Corsini , David Leitsch

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引用次数: 0

Abstract

Objectives

The facultatively anaerobic or microaerophilic bacteria of the genus Gardnerella are the most common species associated with bacterial vaginosis (BV). The treatment of BV is greatly complicated by the high rates of resistance to metronidazole and clindamycin among Gardnerella strains. We wanted to identify factors contributing to metronidazole resistance in G. vaginalis and performed high-throughput mass spectrometry on a selection of susceptible and resistant strains.

Methods

We wanted to identify factors contributing to metronidazole resistance in G. vaginalis and performed high-throughput mass spectrometry on a selection of susceptible and resistant strains.

Results

We identified the downregulation of a novel nitroreductase, GvNR1, as the only relevant change in protein expression in a metronidazole-resistant derivative of the susceptible type of strain ATCC 14018 (emended Gardnerella genospecies 1; i.e. G. vaginalis sensu stricto). When tested in in vitro enzyme assays, GvNR1 displayed very marked nitroreductase activity with several nitro drugs, including metronidazole and other 5-nitroimidazoles. GvNR1 also rendered Escherichia coli BL21-AI much more susceptible to metronidazole when expressed in this strain. In metronidazole-resistant G. vaginalis clinical isolates (>8 µg/mL according to Clinical and Laboratory Standards Institute), GvNR1 was found to be downregulated as well. In resistant clinical strains 33 other proteins were found to be differentially expressed. Of note, these include thioredoxin reductase and vaginolysin. The lowered expression levels of GvNR1 in resistant strains were not caused by mutations in the GvNR1 gene or in sequences directly flanking the gene but by downregulation of mRNA expression. This might explain why G. vaginalis becomes resistant to metronidazole so rapidly.

Conclusions

We propose GvNR1 as a novel metronidazole resistance determinant in G. vaginalis.

Abstract Image

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一种nfsa样的硝基还原酶的下调导致阴道加德纳菌对甲硝唑的耐药性。

加德纳菌属的兼性厌氧或嗜微气细菌是与细菌性阴道病（BV）相关的最常见的物种。由于加特纳菌菌株对甲硝唑和克林霉素的高耐药率，细菌性疱疹的治疗变得非常复杂。我们想要确定影响阴道革螨对甲硝唑耐药的因素，并对敏感和耐药菌株进行高通量质谱分析。因此，我们确定了一种新的硝基还原酶GvNR1的下调是敏感型菌株ATCC 14018（修正的加德纳菌基因种1，即阴道敏感菌）耐甲硝唑衍生物中蛋白表达的唯一相关变化。在体外酶分析中，GvNR1对几种硝基药物（包括甲硝唑和其他5-硝基咪唑）表现出非常显著的硝基还原酶活性。当GvNR1在该菌株中表达时，也使大肠杆菌BL21-AI对甲硝唑更敏感。在耐甲硝唑阴道支原体临床分离株中（根据CLSI， bbb80µg/mL）， GvNR1也被发现下调。在耐药的临床菌株中，还发现了33种其他蛋白的差异表达。值得注意的是，这些包括硫氧还蛋白还原酶和阴道溶素。耐药菌株中GvNR1表达水平的降低不是由GvNR1基因或其直接侧链序列的突变引起的，而是由mRNA表达下调引起的。这也许可以解释为什么阴道支原体对甲硝唑产生抗药性的速度如此之快。我们提出GvNR1作为阴道革螨甲硝唑耐药决定因子。

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来源期刊

International Journal of Antimicrobial Agents 医学-传染病学

CiteScore

21.60

自引率

0.90%

发文量

176

审稿时长

36 days

期刊介绍： The International Journal of Antimicrobial Agents is a peer-reviewed publication offering comprehensive and current reference information on the physical, pharmacological, in vitro, and clinical properties of individual antimicrobial agents, covering antiviral, antiparasitic, antibacterial, and antifungal agents. The journal not only communicates new trends and developments through authoritative review articles but also addresses the critical issue of antimicrobial resistance, both in hospital and community settings. Published content includes solicited reviews by leading experts and high-quality original research papers in the specified fields.