The effect of the clinical phenotype ofMycobacterium aviumcomplex (MAC) lung disease on treatment outcome and redevelopment of nontuberculous mycobacterial (NTM) lung disease after treatment completion has not been studied systematically.We evaluated 481 treatment-naïve patients with MAC lung disease who underwent antibiotic treatment for ≥12 months between January 2002 and December 2013.Out of 481 patients, 278 (58%) had noncavitary nodular bronchiectatic (NB) disease, 80 (17%) had cavitary NB disease and 123 (25%) had fibrocavitary disease. Favourable outcome was higher in patients with noncavitary disease (88%) than in patients with cavitary disease (76% for fibrocavitary and 78% for cavitary NB disease; p<0.05). Cavitary disease was independently associated with unfavourable outcomes (p<0.05). Out of 402 patients with favourable outcomes, 118 (29%) experienced redevelopment of NTM lung disease, with the same MAC species recurring in 65 (55%) patients. The NB form was an independent risk factor for redevelopment of NTM lung disease (p<0.05). In patients with recurrent MAC lung disease due to the same species, bacterial genotyping revealed that 74% of cases were attributable to reinfection and 26% to relapse.Treatment outcomes and redevelopment of NTM lung disease after treatment completion differed by clinical phenotype of MAC lung disease.

Rationale: Patients with refractory Mycobacterium avium complex lung disease (MAC-LD) undergo long-term macrolide therapy, but macrolide resistance develops infrequently. Objectives: The aim of this study was to determine whether reinfection was a factor in the low incidence of macrolide resistance in patients with refractory MAC-LD. Methods: Among 481 patients with treatment-naive MAC-LD who started antibiotic treatment between January 2002 and December 2013, we identified 72 patients with refractory disease, characterized by persistently positive sputum cultures despite ≥12 months of treatment. Molecular analyses of the 23S rRNA gene responsible for macrolide resistance and serial mycobacterial genotyping were performed using stored MAC isolates. Results: The median duration of treatment was 32 months (interquartile range, 24-41 months) in 72 patients. After treatment for a median of 33 months (interquartile range, 21-44 months), macrolide resistance developed in 16 (22%) patients. Molecular analysis of isolates from 15 patients revealed that 80% (12/15) had a point mutation at position 2058 or 2059 of the 23S rRNA gene. Of the 49 patients who had stored pre- and post-treatment isolates, mycobacterial genotyping revealed that reinfection by new MAC strains occurred in 36 (73%) patients. New MAC strains were found in 24 (49%) patients, and mixed infections with original and new strains occurred in 12 (24%) patients. Only 13 (27%) patients had persistent infections with their original MAC strains. Conclusions: Refractory MAC-LD is commonly caused by reinfection with new strains rather than persistence of the original strain, which may explain the infrequent development of macrolide resistance in refractory MAC-LD.

Rationale: Nontuberculous mycobacteria (NTM) are environmental mycobacteria that can cause a chronic progressive lung disease. Although epidemiological data indicate potential genetic predisposition, its nature remains unclear.Objectives: We aimed to identify host susceptibility loci forMycobacterium aviumcomplex (MAC), the most common NTM pathogen.Methods: This genome-wide association study (GWAS) was conducted in Japanese patients with pulmonary MAC and healthy controls, followed by genotyping of candidate single-nucleotide polymorphisms (SNPs) in another Japanese cohort. For verification by Korean and European ancestry, we performed SNP genotyping.Results: The GWAS discovery set included 475 pulmonary MAC cases and 417 controls. Both GWAS and replication analysis of 591 pulmonary MAC cases and 718 controls revealed the strongest association with chromosome 16p21, particularly with rs109592 (p=1.64×10⁻¹³, OR 0.54), which is in an intronic region of the calcineurin-like EF-hand protein 2 (CHP2). Expression quantitative trait loci analysis demonstrated an association with lung CHP2 expression. CHP2 was expressed in the lung tissue in pulmonary MAC disease. This SNP was associated with the nodular bronchiectasis subtype. Additionally, this SNP was significantly associated with the disease in patients of Korean (p=2.18×10⁻¹², OR 0.54) and European (p=5.12×10⁻⁰³, OR 0.63) ancestry.Conclusions: We identified rs109592 in theCHP2locus as a susceptibility marker for pulmonary MAC disease.

Limited data are available regarding the in vitro activity of clofazimine against nontuberculous mycobacteria (NTM) or on outcomes of clofazimine-containing regimens in NTM-pulmonary disease (PD). Therefore, we evaluated the in vitro activity of clofazimine and the clinical outcomes of clofazimine-containing regimens. We evaluated clofazimine in vitro activity for 303 NTM isolates from NTM-PD patients. Fifty-seven clarithromycin-resistant and 35 amikacin-resistant isolates were also analyzed. Culture conversion after a 12-month treatment regimen containing clofazimine was evaluated in 58 NTM-PD patients, including 20 patients with drug-resistant isolates. Most of the 303 isolates (238/303) had minimum inhibitory concentrations (MICs) ≤ 0.25 µg/mL for clofazimine (57/63 Mycobacterium avium, 53/57 M. intracellulare, 49/52 M. kansasii, 22/64 M. abscessus, and 57/67 M. massiliense). For the 57 clarithromycin-resistant and 35 amikacin-resistant isolates, most had MICs ≤ 0.25 µg/mL (47/57 and 32/35, respectively). Among the 38 NTM-PD patients without resistance to clarithromycin or amikacin, 47% achieved culture conversion (8/27 M. abscessus, 9/9 M. massiliense, 0/1 M. avium, and 1/1 M. intracellulare). The conversion rate was higher in the MIC ≤ 0.25 µg/mL group than in the MIC = 0.5 µg/mL group (13/18 vs. 5/20, p = 0.004), and an MIC ≤ 0.25 µg/mL remained a significant factor in multivariable analysis. Culture conversion was achieved in 20% of 20 patients with clarithromycin- or amikacin-resistant isolates. However, a clofazimine MIC ≤ 0.25 µg/mL was not significant for culture conversion in the 58 NTM-PD patients, regardless of the drug resistance pattern. Clofazimine was effective in vitro against NTM species. Some patients on clofazimine-containing regimens achieved culture conversion.

Infections caused by nontuberculous mycobacteria have increased more than 50% in the past two decades and more than doubled in the elderly population. Mycobacterium abscessus (Mab), one of the most prevalent of these rapidly growing species, is intrinsically resistant to numerous antibiotics. Current standard-of-care treatments are not satisfactory, with high failure rate and notable adverse effects. We report here a potent anti-Mab compound from the flexible molecular framework afforded by conjugated oligoelectrolytes (COEs). A screen of structurally diverse, noncytotoxic COEs identified a lead compound, COE-PNH ₂ , which was bactericidal against replicating, nonreplicating persisters and intracellular Mab.COE-PNH ₂ had low propensity for resistance development, with a frequency of resistance below 1.25 × 10 ⁻⁹ and showed no detectable resistance upon serial passaging. Mechanism of action studies were in line with COE-PNH ₂ affecting the physical and functional integrity of the bacterial envelope and disrupting the mycomembrane and associated essential bioenergetic pathways. Moreover, COE-PNH ₂ was well-tolerated and efficacious in a mouse model of Mab lung infection. This study highlights desirable in vitro and in vivo potency and safety index of this COE structure, which represents a promising anti-mycobacterial to tackle an unmet medical need.

Bearing strength and fatigue life of pin-loaded glass fibre-reinforced plastics (GFRP) with various interference-fit (I) percentages are experimentally investigated. Stainless steel pins with interference-fits ranging from 0 per cent to 2 per cent are inserted into vacuum infusion-processed GFRP. After pin installation, damage in the composite hole is observed. The quasi-static and fatigue properties of the pin-loaded composites with interference-fits (I = 0.6 per cent, 1 per cent, and 2 per cent) are then compared to samples with transition-fit (I = 0 per cent). The experimental results showed that interference-fit of 0.6 per cent and 1 per cent improved bearing strength slightly and fatigue life significantly when compared with transition-fit of 0 per cent. Bearing strength was decreased with 2 per cent interference-fit due to GFRP damage induced during pin installation. The sample with I = 0.6 per cent attains the longest fatigue life and provides the most reliable results, with the least amount of scatter.