Guo Qi, Chen Jianhui, Zhang Shaoyan, Zou Yuzhen, Zhang Yongjie, Huang Dongdong, Zhang Zhemin, Li Bing, Chu Haiqing
Department of Respiratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People's Republic of China.
Tongji University School of Medicine, Shanghai 200092, People's Republic of China.
Infect Drug Resist. 2020 Feb 12;13:447-454. doi: 10.2147/IDR.S239850. eCollection 2020.
The emergence of clarithromycin resistance is a challenge in treating infections. Known mechanisms that contribute to intrinsic clarithromycin resistance focus on gene-related mutations, but resistant clinical isolates often exhibit an inconsistent genotype.
In this study, 194 clinical isolates were collected from patients with lung infections and the whole genome of each isolate was sequenced. A comprehensive examination of the molecular mechanisms underlying intrinsic clarithromycin resistance was performed, combining MIC determination, comparative genome sequence analysis and qRT-PCR.
Of the 194 isolates, 13 (6.7%) were clarithromycin resistant; only seven of these harbored a 2270/2271 mutation. The remaining six resistant isolates did not exhibit a specific resistance-associated mutation in the clarithromycin target-site genes, and , or in the modification gene (41). qRT-PCR analysis showed that the increased expression of the efflux pump genes, MAB_2355c, MAB_1409c and MAB_1846, as well as their positive regulatory gene , consistently correlated with increased clarithromycin resistance. The presence of efflux pump inhibitors significantly decreased the MIC of clarithromycin for nonsusceptible isolates, especially the intrinsic resistant isolates that exhibited no 2270/2271 mutation.
These findings indicate that efflux pumps play a prominent role in the intrinsic resistance of to clarithromycin, complementing other known resistance mechanisms.
克拉霉素耐药性的出现是治疗感染的一项挑战。已知导致固有克拉霉素耐药性的机制主要集中在基因相关突变上，但耐药临床分离株的基因型往往不一致。
本研究收集了194例肺部感染患者的临床分离株，并对每个分离株的全基因组进行测序。结合最低抑菌浓度（MIC）测定、比较基因组序列分析和定量逆转录聚合酶链反应（qRT-PCR），对固有克拉霉素耐药性的分子机制进行了全面研究。
在194株分离株中，13株（6.7%）对克拉霉素耐药；其中只有7株存在2270/2271突变。其余6株耐药分离株在克拉霉素靶位点基因、和/或修饰基因（41）中未表现出特定的耐药相关突变。qRT-PCR分析表明，外排泵基因MAB_2355c、MAB_1409c和MAB_1846及其正向调节基因的表达增加与克拉霉素耐药性增加始终相关。外排泵抑制剂的存在显著降低了克拉霉素对非敏感分离株的MIC，尤其是对未发生2270/2271突变的固有耐药分离株。
这些发现表明，外排泵在肺炎支原体对克拉霉素的固有耐药性中起重要作用，补充了其他已知的耐药机制。
