Clinical significance of nontuberculous mycobacteria isolates in elderly Taiwanese patients.

The aim of this study was to investigate the clinical significance of nontuberculous mycobacteria (NTM) isolates in elderly Taiwanese patients. From 2004 through 2008, patients >65 years old with NTM isolation were identified. The definitions of NTM disease followed the American Thoracic Society and Infectious Disease Society of America (ATS/IDSA) criteria. Among the 3,175 NTM isolates, Mycobacterium avium complex (MAC; n = 1,118, 35.2%) was the most prevalent species, followed by M. abscessus (n = 545, 17.2%). Among the 1,633 elderly patients with NTM isolates, the most prevalent NTM species were MAC (n = 592, 36.3%) and M. fortuitum complex (n = 311, 19.0%). NTM colonization was found in 1,339 (80.4%) patients and only 326 (19.6%) patients had NTM diseases. During the study period, the annual incidence rates (per 100,000 inpatients and outpatients) of NTM colonization and disease both increased significantly (p < 0.0001) from 10.5 to 15.8 and from 2.1 to 4.3, respectively. Isolated pulmonary NTM infections compromised 294 (90.2%) of the 326 elderly cases of NTM disease. In conclusion, this study found an increasing trend in the incidence of both NTM isolates and NTM diseases among elderly Taiwanese patients. MAC and M. abscessus were the most frequent species causing various types of NTM disease.