Previously, we characterized 7C, a laboratory-derived tigecycline-resistant mutant of Mycobacterium abscessus ATCC 19977, and found that the resistance was conferred by a mutation in MAB_3542c, which encodes an RshA-like protein. In M. tuberculosis, RshA is an anti-sigma factor that negatively regulates the SigH-dependent heat/oxidative stress response. We hypothesized that this mutation in 7C might dysregulate the stress response which has been generally linked to antibiotic resistance. In this study, we tested this hypothesis by subjecting 7C to transcriptomic dissection using RNA sequencing. We found an over-expression of genes encoding the SigH ortholog, chaperones and oxidoreductases. In line with these findings, 7C demonstrated better survival against heat shock when compared to the wild-type ATCC 19977. Another interesting observation from the RNA-Seq analysis was the down-regulation of ribosomal protein-encoding genes. This highlights the possibility of ribosomal conformation changes which could negatively affect the binding of tigecycline to its target, leading to phenotypic resistance. We also demonstrated that transient resistance to tigecycline could be induced in the ATCC 19977 by elevated temperature. Taken together, these findings suggest that dysregulated stress response may be associated with tigecycline resistance in M. abscessus.

以前，我们对7C（实验室衍生的脓肿分枝杆菌ATCC 19977的替加环素抗性突变体）进行了表征，发现该抗性是由MAB_3542c中的突变赋予的，该突变体编码RshA样蛋白。在结核分枝杆菌中RshA是一种反西格玛因子，可负调节SigH依赖的热/氧化应激反应。我们假设7C中的这种突变可能会失调应激反应，而这种应激反应通​​常与抗生素耐药性有关。在这项研究中，我们通过使用RNA测序对7C进行转录组解剖来验证了这一假设。我们发现编码SigH直系同源基因，伴侣和氧化还原酶的基因过表达。符合这些发现，与野生型ATCC 19977相比，7C表现出更好的抗热休克能力。RNA-Seq分析的另一个有趣观察结果是核糖体蛋白编码基因的下调。这突显了核糖体构象变化的可能性，该变化可能会对替加环素与其靶标的结合产生负面影响，导致表型耐药。我们还证明，升高温度可在ATCC 19977中诱导出对替加环素的瞬时耐药性。综上所述，这些发现表明应激反应失调可能与替加环素耐药有关。脓肿。