Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
Research and Diagnostic Center for Emerging Infectious Diseases (RCEID), Khon Kaen University, Khon Kaen, Thailand.
PLoS One. 2023 Nov 22;18(11):e0294677. doi: 10.1371/journal.pone.0294677. eCollection 2023.
Mycobacterium avium complex (MAC) infections are a significant clinical challenge. Determining drug-susceptibility profiles and the genetic basis of drug resistance is crucial for guiding effective treatment strategies. This study aimed to determine the drug-susceptibility profiles of MAC clinical isolates and to investigate the genetic basis conferring drug resistance using whole-genome sequencing (WGS) analysis. Drug-susceptibility profiles based on minimum inhibitory concentration (MIC) assays were determined for 38 MAC clinical isolates (12 Mycobacterium avium and 26 Mycobacterium intracellulare). Mutations associated with drug resistance were identified through genome analysis of these isolates, and their phylogenetic relationships were also examined. Drug resistance, based on MIC values, was most commonly observed for moxifloxacin (81.6%), followed by linezolid (78.9%), clarithromycin (44.7%) and amikacin (36.8%). We identified specific mutations associated with resistance to amikacin. These include the rrs mutation at C464T in amikacin intermediate-resistance M. avium, and two mutations at T250A and G1453T in amikacin non-susceptible M. intracellulare. Mutations in rrl at A2058G, A2059C and A2059G were potentially linked to clarithromycin resistance. MAC clinical isolates not susceptible to linezolid exhibited mutations in rplC at G237C and C459T, as well as two rplD mutations at G443A and A489G. GyrB substitution Thr521Ala (T521A) was identified in moxifloxacin non-susceptible isolates, which may contribute to this resistance. A phylogeny of our MAC isolates revealed high levels of genetic diversity. Our findings suggest that the standard treatment regimen for MAC infections using moxifloxacin, linezolid, clarithromycin and amikacin may be driving development of resistance, potentially due to specific mutations. The combination of phenotypic and genotypic susceptibility testing can be valuable in guiding the clinical use of drugs for the treatment of MAC infections.
鸟分枝杆菌复合体（MAC）感染是一个重大的临床挑战。确定药物敏感性谱和耐药性的遗传基础对于指导有效的治疗策略至关重要。本研究旨在确定 MAC 临床分离株的药物敏感性谱，并通过全基因组测序（WGS）分析研究赋予耐药性的遗传基础。基于最小抑菌浓度（MIC）测定法，对 38 株 MAC 临床分离株（12 株鸟分枝杆菌和 26 株胞内分枝杆菌）进行了药物敏感性谱测定。通过对这些分离株的基因组分析确定了与耐药性相关的突变，并检查了它们的系统发育关系。基于 MIC 值，最常见的耐药药物是莫西沙星（81.6%），其次是利奈唑胺（78.9%）、克拉霉素（44.7%）和阿米卡星（36.8%）。我们确定了与阿米卡星耐药相关的特定突变。这些突变包括在阿米卡星中介耐药的鸟分枝杆菌中 rrs 基因的 C464T 突变，以及在阿米卡星非敏感的胞内分枝杆菌中 T250A 和 G1453T 突变。rrl 基因的 A2058G、A2059C 和 A2059G 突变可能与克拉霉素耐药相关。对利奈唑胺不敏感的 MAC 临床分离株表现出 rplC 基因的 G237C 和 C459T 突变，以及 rplD 基因的两个突变 G443A 和 A489G。在对莫西沙星不敏感的分离株中鉴定出 GyrB 基因的 Thr521Ala（T521A）取代，这可能导致了这种耐药性。我们的 MAC 分离株的系统发育树显示出高度的遗传多样性。我们的研究结果表明，使用莫西沙星、利奈唑胺、克拉霉素和阿米卡星治疗 MAC 感染的标准治疗方案可能会导致耐药性的发展，这可能是由于特定的突变。表型和基因型药敏试验的结合可用于指导 MAC 感染治疗药物的临床应用。
