The First Korean Case of Nontuberculous Mycobacterial Lung Disease Caused by Mycobacterium abscessus Subspecies bolletii in a Patient with Bronchiectasis
A 66-year-old male was referred to our hospital for management of probable NTM lung disease. He was an ex-smoker and had a history of previous treatment for pulmonary tuberculosis 10 years prior. Six months before his visit to our hospital, the patient reported chronic cough and sputum. He was initially diagnosed with acid-fast bacilli (AFB) smear-positive pulmonary tuberculosis and received isoniazid, rifampin, ethambutol, and pyrazinamide for 6 months. However, AFB smears were persistently positive, and NTM were cultured from his sputum specimens. He was then referred to our hospital.\nPhysical examination showed that the patient was 172.3 cm tall and weighed 56.1 kg. Laboratory tests results were unremarkable. A human immunodeficiency virus antibody test was negative. The chest radiograph and computed tomography (CT) scan revealed multifocal bronchiectasis and bronchiolitis in both lungs that suggested the nodular bronchiectatic form of NTM lung disease ().\nThe patient's sputum was positive for AFB staining, and NTM were isolated more than three times in a liquid culture system (Bactec MGIT 960 system; BD Diagnostics, Sparks, MD, USA). To identify the etiological agent, bacteria were initially propagated in 7H9 broth (Difco Laboratories, Detroit, MI, USA) supplemented with 10% (vol/vol) oleic acid-albumin-dextrose-catalase (BD Diagnostics) for 7 days at 37℃, sub-cultured in egg-based 3% Ogawa solid media (Shinyang, Seoul, Korea), and genomic DNA was extracted from the cultured bacteria. Initial species identification using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method based on the rpoB gene (Myco-ID; M&D Inc., Wonju, Korea) was M. abscessus complex.\nTo speciate the isolates, sequencing analysis of the nearly complete 16S rRNA gene, partial hsp65, and rpoB sequences were performed using GenBank () with the BLAST algorithm. The 16S rRNA sequences showed 100% identity with M. abscessus subsp. abscessus (GenBank accession no. NR074427), M. abscessus subsp. massiliense (GenBank accession no. NR074421), M. chelonae (GenBank accession no. AY457082), and M. abscessus subsp. bolletii (GenBank accession no. NR043236). The hsp65 and rpoB sequences were 100% identical to those of the M. abscessus subsp. bolletii type strain (GenBank accession nos. FJ607778 and AY859692). Phylogenetic analysis based on the rpoB sequences from the isolate SMC-bol-002 and from those of closely related species within the RGM showed that this strain belonged to M. abscessus subsp. bolletii ().\nDrug susceptibility testing was performed using a broth microdilution method (). At the genetic level, the isolate was genotyped for erm(41) polymorphism and for rrl mutations; these are known as the two main mechanisms of macrolide resistance. The isolate had the erm(41) gene with a T28 sequevar and no rrl mutation acquisition.\nThe patient received oral clarithromycin and moxifloxacin, along with an initial 4-week course of intravenous amikacin and cefoxitin. During 4 weeks of initial antibiotic treatment, his symptoms and CT lesions were improved and sputum culture results were negative after 2, 3, and 4 weeks after treatment. Although he took oral clarithromycin and moxifloxacin for a total duration of 24 months, follow-up sputum cultures were persistently positive after 2 months after antibiotic treatment.