The management of multidrug-resistant (MDR) and extensively drug-resistant tuberculosis (XDR-TB) presents a main challenge and the drug options for treating these infections are very limited. Linezolid (LNZ) has recently been approved for the treatment of MDR and XDR-TB. But, there are narrow data on genotypic and phenotypic LNZ resistance in clinical isolates. So, we aimed to determine the prevalence of LNZ resistance and to identify the mutations associated with LNZ resistance among clinical MDR-TB isolates. The minimum inhibitory concentration (MIC) values of LNZ for 22 MDR-TB isolates were determined by broth microdilution method. All MDR-TB isolates were sequenced in the rrl and rplC genes conferring LNZ resistance. LNZ resistance was found in 3 (13.6%) of 22 MDR-TB isolates. The MICs of LNZ were 8 μg/mL for two isolates and 16 μg/mL for one isolate. The 421 (A/G) and 449 (T/A) mutations in rplC gene were detected in one of the LNZ-resistant isolates. There was no mutation in rrl gene. The results reveal that the prevalence of LNZ-resistant isolates is 13.6% among MDR-TB isolates and drug susceptibility testing (DST) against LNZ is useful in the management of complicated and drug-resistant cases. However, further studies could identify other possible genetic mechanism of resistance in TB.

中文翻译：

---

伊朗耐多药结核分枝杆菌临床分离株对利奈唑胺的耐药性。

耐多药 (MDR) 和广泛耐药结核病 (XDR-TB) 的管理是一项主要挑战，治疗这些感染的药物选择非常有限。利奈唑胺（LNZ）最近被批准用于治疗耐多药和广泛耐药结核病。但是，关于临床分离株中基因型和表型 LNZ 耐药性的数据很少。因此，我们旨在确定 LNZ 耐药性的流行情况，并确定临床 MDR-TB 分离株中与 LNZ 耐药性相关的突变。LNZ 对 22 株耐多药结核病菌株的最低抑菌浓度 (MIC) 值通过肉汤微量稀释法测定。所有 MDR-TB 分离株都在赋予 LNZ 抗性的 rrl 和 rplC 基因中进行了测序。在 22 个 MDR-TB 分离株中的 3 个（13.6%）中发现了 LNZ 耐药性。两种分离株的 LNZ MIC 为 8 μg/mL，一种分离株的 MIC 为 16 μg/mL。在 LNZ 抗性分离株之一中检测到 rplC 基因的 421 (A/G) 和 449 (T/A) 突变。rrl基因无突变。结果表明，耐多药结核病菌株中 LNZ 耐药菌株的流行率为 13.6%，针对 LNZ 的药敏试验 (DST) 可用于复杂和耐药病例的管理。然而，进一步的研究可以确定其他可能的结核病耐药遗传机制。MDR-TB 分离株中的 6% 和针对 LNZ 的药敏试验 (DST) 可用于管理复杂和耐药病例。然而，进一步的研究可以确定其他可能的结核病耐药遗传机制。MDR-TB 分离株中的 6% 和针对 LNZ 的药敏试验 (DST) 可用于管理复杂和耐药病例。然而，进一步的研究可以确定其他可能的结核病耐药遗传机制。