Introduction. Tigecycline is currently acknowledged to be one of the most effective antibiotics against infections caused by Mycobacteroides abscessus . Gap statement. The genetic determinants of tigecycline resistance in M. abscessus are not well understood. Aim. In this study, we characterized a tigecycline-resistant M. abscessus mutant, designated CL7, to identify the potential resistance mechanism. Methodology. CL7 was characterized using antimicrobial susceptibility testing, whole-genome sequencing, PCR and RT-qPCR. For biological verification, gene overexpression assays were carried out. Results. Whole-genome sequencing and the subsequent gene overexpression assays showed that CL7 harboured a stop–gain mutation in MAB_3543 c, which may be responsible for the tigecycline resistance phenotype. This gene encodes an orthologue of SigH, which is involved in the positive regulation of physiological stress response and is negatively regulated by the RshA anti-sigma factor in Mycobacterium tuberculosis . We hypothesized that the MAB_3543 c mutation may disrupt the interaction between SigH and RshA (MAB_3542 c). RT-qPCR analyses revealed the upregulation of MAB_3543 c and other key stress response genes, which has previously been shown to be a hallmark of SigH–RshA bond disruption and tigecycline resistance. Conclusion. The MAB_3543c mutation may represent a novel determinant of tigecycline resistance in M. abscessus . The findings of this study will hopefully contribute to our knowledge of potential tigecycline resistance mechanisms in M. abscessus , which may lead to better diagnostics and treatment modalities in the future.

中文翻译：

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西格玛因子 SigH (MAB_3543c) 的停止增益突变可能与分枝杆菌脓肿中的替加环素耐药有关

介绍。替加环素目前被公认为是对抗分枝杆菌脓肿感染最有效的抗生素之一。间隙声明。脓肿分枝杆菌中替加环素抗性的遗传决定因素尚不清楚。目标。在这项研究中，我们表征了一种名为 CL7的抗替加环素M. abscessus突变体，以确定潜在的抗性机制。方法。CL7 的特征是使用抗菌药物敏感性测试、全基因组测序、PCR 和 RT-qPCR。为了生物学验证，进行了基因过表达测定。结果。 全基因组测序和随后的基因过表达分析表明，CL7 在MAB_3543 c 中存在停止增益突变，这可能是替加环素抗性表型的原因。该基因编码 SigH 的直向同源物，其参与生理应激反应的正调控，并受结核分枝杆菌中RshA 抗 sigma 因子的负调控。我们假设 MAB_3543 c 突变可能会破坏 SigH 和 RshA (MAB_3542 c) 之间的相互作用。RT-qPCR 分析揭示了MAB_3543 c 和其他关键应激反应基因的上调，这之前已被证明是 SigH-RshA 键破坏和替加环素抗性的标志。结论。 MAB_3543c 突变可能代表脓肿分枝杆菌中替加环素耐药性的新决定因素。这项研究的结果有望有助于我们了解M. abscessus中潜在的替加环素耐药机制，这可能会导致未来更好的诊断和治疗方式。