Infectious and Tropical Diseases Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Department of Microbiology, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
PLoS One. 2022 Aug 12;17(8):e0267320. doi: 10.1371/journal.pone.0267320. eCollection 2022.
Among Non-tuberculous mycobacteria (NTM) which generally cause opportunistic infections, especially in immunocompromised hosts, Mycobacterium simiae (M. simiae) is one of the most important NTM, associated with pulmonary disease. The main concern about M. simiae infections is the extreme resistance of this NTM to antibiotics. There are limited studies about drug susceptibility testing (DST) and the causes of drug resistance in M. simiae. Hence, the current study aimed to identify the M. simiae isolates and to assess the drug resistance of the isolates using phenotypic and molecular methods.
In this study, 50 clinical pulmonary isolates suspected of NTM were collected from regional tuberculosis reference laboratories in Iran. The isolates were identified as M. simiae by using standard biochemical tests and molecular methods. DST was performed for identified M. simiae isolates and additional 35 M. simiae isolates from the department archive, against eight drugs. The mutations in gyrA, gyrB, and rrl genes in clarithromycin and moxifloxacin resistant isolates were investigated by polymerase chain reaction (PCR) followed by sequencing.
Out of 50 suspected NTM isolates, 25 isolates were detected as M. simiae species based on the biochemical tests, and 18 isolates were verified based on the rpoB gene sequence analysis to achieve a total of 53 isolates when the archive isolates were included. DST results showed that all 53 isolates were resistant to isoniazid, rifampin, and clofazimine. The rate of resistance to ethambutol and linezolid were 34 (64%), and 40 (76%) respectively. The highest susceptibility rate was demonstrated for amikacin 53 (100%) and clarithromycin 45(85%), followed by moxifloxacin 35(66%). Sequence analysis showed mutations in positions 2058 and 2059 of the rrl gene, as well non-synonymous mutation at codons 389, 444, and 571 of the gyrB gene. Sequence analysis showed no mutation in the gyrA gene. drug-resistant isolates with mutations showed higher MICs compared to non-mutant resistant isolates.
This study revealed amikacin, clarithromycin, and moxifloxacin as the most effective antibiotics. However, since M. simiae exhibited a high level of antibiotic resistance in vitro, therefore, species identification and determining the antibiotic susceptibility pattern of the isolates are essential before treatment.
分枝杆菌（NTM）通常会引起机会性感染，尤其是在免疫功能低下的宿主中。其中，猿分枝杆菌（M. simiae）是最重要的 NTM 之一，与肺部疾病有关。人们主要关注的是这种 NTM 对抗生素的极度耐药性。关于 M. simiae 感染的药敏试验（DST）和耐药原因的研究有限。因此，本研究旨在通过表型和分子方法鉴定 M. simiae 分离株并评估分离株的耐药性。
本研究从伊朗地区结核病参考实验室收集了 50 株疑似非结核分枝杆菌的临床肺部分离株。通过标准生化试验和分子方法鉴定为 M. simiae。对鉴定为 M. simiae 的分离株以及来自系档案的另外 35 株 M. simiae 分离株进行药敏试验，共 8 种药物。通过聚合酶链反应（PCR）和测序检测克拉霉素和莫西沙星耐药分离株中 gyrA、gyrB 和 rrl 基因的突变。
50 株疑似非结核分枝杆菌的分离株中，25 株经生化试验鉴定为 M. simiae 种，18 株经 rpoB 基因序列分析鉴定，共 53 株。当包括档案分离株时，DST 结果显示，所有 53 株分离株均对异烟肼、利福平、氯法齐明耐药。乙胺丁醇和利奈唑胺的耐药率分别为 34（64%）和 40（76%）。对阿米卡星的敏感性最高，为 53（100%），对克拉霉素的敏感性为 45（85%），其次是莫西沙星，为 35（66%）。序列分析显示 rrl 基因 2058 和 2059 位的突变以及 gyrB 基因 389、444 和 571 位的错义突变。gyrA 基因未发生突变。突变耐药分离株的 MIC 值高于非突变耐药分离株。
本研究表明阿米卡星、克拉霉素和莫西沙星是最有效的抗生素。然而，由于 M. simiae 体外表现出高水平的抗生素耐药性，因此在治疗前必须进行物种鉴定和确定分离株的抗生素药敏模式。
