Increasing patients with pulmonary Mycobacterium avium complex disease and associated underlying diseases in Japan

This study was conducted to evaluate trends in the isolation of strains of nontuberculous mycobacteria (NTM) and trends in the number of patients with pulmonary Mycobacterium avium complex (MAC) disease. We retrospectively reviewed microbiological results and clinical data to identify patients who were diagnosed with pulmonary MAC disease at Kyoto University Hospital in Japan between 2000 and 2013. NTM were isolated from 6327 of 80,285 samples (7.9%) for mycobacterial culture. The proportion of NTM isolates among all mycobacterial isolates increased from 355 of 792 samples (44.8%) in 2000 to 688 of 847 samples (81.2%) in 2013. MAC was most frequently observed (5436 isolates, 85.9%), followed by Mycobacterium abscessus (175 isolates, 2.8%) and Mycobacterium kansasii (74 isolates, 1.2%). A total of 592 patients with pulmonary MAC disease were identified (age, 66.0 ± 11.5 years; females, 61.1%). Compared with the early cohort (2000-2006, 236 patients), more patients in the late cohort (2007-2013, 356 patients) had an underlying disease (157 [66.5%] vs. 284 [79.8%], P = 0.0003), a Charlson comorbidity index score ≥ 1 (115 [48.7%] vs. 213 [59.8%], P = 0.008), collagen vascular disease (18 [7.6%] vs. 60 [16.9%], P = 0.001), rheumatoid arthritis (11 [4.7%] vs. 41 [11.5%], P = 0.004), and used immunosuppressive drugs (22 [9.3%] vs. 63 [17.7%], P = 0.004). The numbers of patients with lung disease, malignant disease and diabetes mellitus increased; however, their frequencies did not differ. The recovery rate of NTM and patients with pulmonary MAC disease increased, especially in patients with collagen vascular disease or rheumatoid arthritis or who used immunosuppressive drugs.