Infection and Drug Resistance (Feb 2020)
Efflux Pumps Contribute to Intrinsic Clarithromycin Resistance in Clinical, Mycobacterium abscessus Isolates
Abstract
Qi Guo,1,2 Jianhui Chen,1,2 Shaoyan Zhang,1 Yuzhen Zou,1,2 Yongjie Zhang,1,2 Dongdong Huang,1 Zhemin Zhang,1 Bing Li,1 Haiqing Chu1,3 1Department of Respiratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People’s Republic of China; 2Tongji University School of Medicine, Shanghai 200092, People’s Republic of China; 3Shanghai Key Laboratory of Tuberculosis, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People’s Republic of ChinaCorrespondence: Haiqing Chu; Bing LiDepartment of Respiratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, No. 507 Zhengmin Road, Shanghai 200433, People’s Republic of ChinaTel/Fax +86 021 6511 5006Email [email protected]; [email protected]: The emergence of clarithromycin resistance is a challenge in treating Mycobacterium abscessus infections. Known mechanisms that contribute to intrinsic clarithromycin resistance focus on rrl gene-related mutations, but resistant clinical isolates often exhibit an inconsistent rrl genotype.Patients and Methods: In this study, 194 clinical Mycobacterium abscessus 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.Results: Of the 194 isolates, 13 (6.7%) were clarithromycin resistant; only seven of these harbored a rrl 2270/2271 mutation. The remaining six resistant isolates did not exhibit a specific resistance-associated mutation in the clarithromycin target-site genes, rrl, rplC, rplD and rplV, or in the rrl modification gene erm(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 whiB7, 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 rrl 2270/2271 mutation.Conclusion: These findings indicate that efflux pumps play a prominent role in the intrinsic resistance of M. abscessus to clarithromycin, complementing other known resistance mechanisms.Keywords: Mycobacterium abscessus, clarithromycin resistance, efflux pumps
