Nontuberculous Mycobacterial Lung Disease Caused by Mycobacterium chelonae: A Case Report
In April 2008, a 69-year-old woman was referred to our hospital because of hemoptysis. She had been healthy until one month prior, when intermittent hemoptysis developed. The patient had no smoking history or other medical history. On examination, the patient appeared well. Her weight was 45 kg, height 156.2 cm, temperature 36.2℃, blood pressure 133/75 mm Hg, pulse 73 beats per minute, and oxygen saturation 100% while breathing ambient air. Laboratory results were normal. A human immunodeficiency virus antibody test was negative.\nA computed tomography (CT) scan of the chest revealed bronchiectasis and bronchiolitis in the lingular division of the left upper lobe (). There was no evidence of cystic fibrosis or other common causes of bronchiectasis. NTM were isolated three times from sputum specimens.\nNTM species were identified using a polymerase chain reaction-restriction fragment length polymorphism analysis (PRA) based on the partial region of the rpoB gene. Colonies were scraped, and genomic DNA of the isolate was extracted using a commercial kit (QIAamp DNA Mini kit; Qiagen, Hilden, Germany). Amplification of the partial rpoB gene (360 bp) was performed using primers Rpo5' (5'-TCAAGGAGAAGCGCTACGA-3') and Rpo3' (5'-GGATGTTGATCAGGGTCTGC-3') with subsequent digestion with 5 units of Msp I (New England BioLabs, Beverly, MA, USA) for 3 hours at 37℃. The digestion mixtures were analyzed by 3% (w/v) agarose gel electrophoresis. DNA size markers, pBR322-MspI-digested DNA (New England BioLabs) were used to enable estimation of DNA fragment size. The PRA results were determined by comparing their restriction patterns with those available in the National Center for Biotechnology Information GenBank database and referred to as described by Lee et al. for the rpoB-PRA. The rpoB amplicon restricted by MspI resulted in fragment sizes of 105, 95, 80, 50, and 40 bp in two serial cultures (). The rpoB-PRA patterns of those cultures exactly matched the known restriction fragment pattern of the reference strain of M. chelonae subsp. chelonae ATCC35749.\nThe identification of these NTM isolates was further confirmed by DNA sequence analysis of the partial rpoB gene (723 bp) using primers MycoF (5'-GGCAAGGTCACCCCGAAGGG-3') and MycoR (5'-AGCGGCTGCTGGGTGATCATC-3') and the partial hsp65 gene (439 bp) using primers Tb11 (5'-ACCAACGATGGTGTGTCCAT-3') and Tb12 (5'-CTTGTCGAACCGCATACCCT-3'). The results revealed sequence similarity (above 99.9%) with M. chelonae for the rpoB gene (GenBank accession no. EU109300.1) and hsp65 gene (GenBank accession no. U55832).\nFinally, the patient was diagnosed with M. chelonae lung disease. Antibiotic therapy was not initiated because of her mild symptoms. Three years after diagnosis of M. chelonae lung disease, follow-up chest CT was performed. Although there was mild progression of peribronchial infiltration on the lingular division of the left upper lobe and newly appeared bronchiolitis in the superior segment of the left lower lobe (), she did not complain of aggravation of her symptoms.