Clinical Implications of The Isolation of Rare Nontuberculous Mycobacteria (NTM)

Abstract

Introduction: The isolation of nontuberculous mycobacteria (NTM) from humans has been increasing. Although the clinical implications of common NTM are well-known, the importance of the rare NTM remains unclear. We investigated the clinical implication of the rare NTM.

Methods: Patients with NTM isolation between July 1, 2010, and June 31, 2012, were screened for inclusion. Rare NTM were defined as NTM classes except the seven commonly identified NTM species at Seoul National University Hospital: Mycobacterium. avium, M. intracellulare, M. abscessus, M. massilence, M. fortuitum, M. kansasii, and M. gordonae. Clinical, radiographic, and microbiological data of patients with rare NTM were reviewed and analyzed.

Results: During the study period, 2,556 NTM were isolated from 1,373 patients. Of 2,556 NTM, species identifications of 805 NTM were performed. Ninety NTM from 84 patients were identified as rare NTM. Among these, M. peregrinum was the most common (17 times, 18.5%). The median age of 84 patients was 64 years (range, 26-84 years), and 50 (59.5%) patients were male. The most common underlying diseases were solid organ malignancies, including lung cancer (12 patients, 14.3 %). Sputum (54.8%) and cough (47.6%) were the most common symptom complaints. On radiologic findings, both upper lobes were commonly involved lesions (right upper lobe in 46 patients and left upper lobe in 40 patients). Multiple nodules were the most commonly observed radiographic findings (49 patients, 58.3%) followed by bronchiectasis (27 patients, 32.1 %) and cavities (16 patients, 19.0 %). Among five patients in whom rare NTM were isolated twice or more times, one in whom rare NTM as well as M. abscessus were isolated had progression of radiographic findings and symptoms. In the other three patients, neither aggravation of symptoms nor progression of radiography lesions on chest radiography developed. The other patient in whom M. chimaera were isolated three times, developed new centrilobular nodules. However, the symptoms of this patient did not change.

Conclusions: Most of the rarely identified NTM species were identified only once in patients followed by rare clinical aggravation. Clinicians should observe these patients closely without invasive work ups.