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Siyuan He,1,2,* Yuzhen Zou,1,2,* Mengling Zhan,1,2,* Qi Guo,1,2 Yongjie Zhang,1,2 Zhemin Zhang,1 Bing Li,1 Shaoyan Zhang,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 China*These authors contributed equally to this workCorrespondence: Haiqing Chu; Shaoyan ZhangDepartment of Respiratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, No. 507 Zhengmin Road, Shanghai 200433, People’s Republic of ChinaTel/ Fax +86 21 6511 5006Email chu_haiqing@126.com; zhangshaoyan000@163.comPurpose: Imipenem is one of the very few effective options for treating Mycobacterium abscessus (M. abscessus) infections; the development of imipenem resistance is a major health concern.Materials and Methods: The susceptibility of 194 clinical M. abscessus isolates to imipenem was determined. The ability of imipenem to synergize with N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), a zinc chelator and a metallo-β-lactamases (MBLs) inhibitor, to inhibit M. abscessus growth was also assessed.Results: M. abscessus exhibited an elevated resistance to imipenem (MIC50 = 16 mg/L, MIC90 = 64 mg/L). A combination of TPEN and imipenem synergized to inhibit the growth of 100% of imipenem-resistant and 79.2% of imipenem-resistance intermediate isolates; no synergy was observed treating imipenem-sensitive isolates. A remarkable decrease in the MIC50 (from 16 to 4 mg/L) and MIC90 (from 64 to 8 mg/L) of imipenem was observed when it was combined with TPEN; the portion of imipenem-resistant isolates also decreased (from 48.4% to 0%). Consistent with these results demonstrating synergy, a time-kill assay showed the addition of TPEN significantly improved the bactericidal activity of imipenem toward M. abscessus. Similarly, EDTA (a potent MBLs inhibitor) promoted the anti-M. abscessus activity of imipenem in a disk assay, corroborating the effect of TPEN and supporting the role of MBLs in imipenem resistance exhibited by some isolates.Conclusion: These findings demonstrate that TPEN can reduce the resistance of M. abscessus to imipenem and suggest that the inhibition of MBLs activity is the underlying mechanism.Keywords: Mycobacterium abscessus, TPEN, imipenem resistance, metallo-β-lactamases

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 chu_haiqing@126.com; libing044162@163.comPurpose: 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

Introduction Nontuberculous mycobacteria (NTM) have emerged as critical opportunistic pathogens of lung diseases recently. Patients with preexisting bronchiectasis are susceptible to NTM. Nevertheless, patients with preexisting bronchiectasis are susceptible to NTM but the prevalence of NTM pulmonary infection in different species and geographical areas is still not fully understood. Material and methods The relevant data of the prevalence of NTM in patients with bronchiectasis were retrieved by searching the main databases such as PubMed, MEDLINE, Cochrane Library, and EMBASE. This meta-analysis was performed using Rev. Man 5.1 and Stata 11.0 software. The collected information of NTM prevalence was chosen as the effect size. Results The results of the meta-analysis showed that the overall prevalence of NTM was 9.3% in patients with bronchiectasis. The further stratification of subgroup analysis indicated that the combined prevalence of NTM was higher in studies whose “sample size” was more than or equal to 100 (p = 0.002), in studies in which “time of study” was after or equal to 2002 (p < 0.001), in studies in which “participants’ geographic location” was Asian (p < 0.001) and in studies whose “method of study” was retrospective (p = 0.002) as well, compared with corresponding groups. Conclusions Our findings suggested that the prevalence NTM infection is high in patients with bronchiectasis. A larger number of definitive randomized trials are still required to assess this research issue.

The aim of the study was to investigate the epidemic characteristics of Mycobacterium abscessus in Shanghai. Fifty-five strains from 55 M. abscessus pulmonary disease patients were isolated. Drug sensitivity was measured by a broth microdilution method. Subtypes of M. abscessus were identified by DNA sequencing. Multilocus sequence typing (MLST), mining spanning tree (MST), and pulsed-field gel electrophoresis (PFGE) were used to analyze sequence types (ST) and clonal complexes (CC). Clinical manifestations were assessed by CT imaging. We identified 42 A isolates, 11 M, and 2 B-subtypes. A and M were highly sensitive to tigecycline and amikacin (97.6–100%). The A-type easily developed drug resistance against clarithromycin. Both types were highly resistance to sulfonamides, moxifloxacin, doxycycline, imipenem, and tobramycin. MLST analysis identified 41 STs including 32 new STs. The MST algorithm distributed 55 isolates into 12 separate CC. The PFGE analysis exhibited 53 distinct restriction patterns and the M-type was closely clustered according to their ST and CC numbers. CT imaging showed that tree-in-bud and patch shadow were commonly observed in M-type, whereas pulmonary cavities were often found in A-type infection patients (P