铁摄取转录因子FurB调控VII型分泌系统介导脓肿分枝杆菌对贝达喹啉耐药的机制研究

Infections caused by Mycobacterium abscessus (Mab) are difficult to treat. Bedaquiline (BDQ) is a newly approved effective antibiotic for the treatment of Mab infections. However, BDQ-resistant Mab clinical isolates have emerged. The mechanism of BDQ resistance in Mab is virtually unknown and urgently needed to be fully elucidated. Taking advantages of the resource in Pulmonary Specialty Hospital, we longitudinally collected a series of Mab clinical isolates from patients. Using whole-genome sequencing and comparative analyses, we discovered, for the first time, that furB mutation and WhiB6 over expression were specifically exist in the BDQ-resistant strains that couldn’t be explained by currently known mechanisms. We assumed that “FurB-WhiB6-Type VII secretion system” signaling pathway was involved in the BDQ resistance. Activation of this pathway may lead to elevated secretion of the BDQ-protein complex, reducing the intracellular BDQ concentration, and eventually resulted in BDQ resistance. However, the exact factors and molecular mechanisms of this pathway in BDQ resistance have not been fully clarified yet, which require further investigation. We will perform gene knock out/in, secretory omics, isothermal titration calorimetry, electrophoretic mobility shift assay and other experiments, to confirm the exact subtype of Type VII secretion system contributing to the BDQ resistance, identify the secreted proteins that bind to BDQ, elucidated the underlying regulation mechanism of this pathway in BDQ resistance, and analysis the incidence and epidemiological characteristics of this pathway in BDQ-resistant Mab clinical isolates. Outcomes from this project will have great scientific and clinical significance in prevention and treatment of drug-resistant Mab infections.

脓肿分枝杆菌（Mab）感染治疗困难，贝达喹啉（BDQ）是治疗Mab感染的有效新药，但也出现了临床耐药株。目前对BDQ耐药机制知之甚少，亟待深入研究。依托所在专科医院的资源优势，申请者收集了系列Mab临床株，通过全基因组比对分析，首次发现furB基因突变伴WhiB6高表达特异地存在于已知机制无法解释的BDQ耐药株，初步判断“FurB-WhiB6-VII型分泌系统”信号通路参与BDQ耐药，此通路激活可导致与BDQ结合的分泌蛋白向细胞外转运，降低细胞内药物浓度而引起耐药。但通路中各因子及其调控的分子机制需进一步明确。本课题拟通过基因敲除、组学测序、凝胶迁移、等温滴定量热法等试验，明确参与BDQ耐药的VII型分泌系统亚型，鉴定与BDQ结合的分泌蛋白，揭晓该通路调控BDQ耐药的分子机制，并分析该通路在BDQ耐药Mab中的流行病学特点，研究成果有助于耐药Mab感染的防治，具有重要科学意义和实用价值。

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