Epidemiology and clinical features of nontuberculous mycobacterial lung disease in a subtropical region in Japan: Analysis with a 7-year data in two major hospitals

Abstract

Background: NTM (nontuberculous mycobacteria) is ubiquitous bacteria and widely distributed. Additionally, the species isolated from patients with NTM lung disease are geographically diverse. In this study, the epidemiology and clinical features of NTM lung disease in Okinawa, a subtropical region in Japan, were retrospectively analyzed. Method: Between Jan. 2009 and Dec. 2015, laboratory examinations detected NTM from respiratory specimens from Okinawa Chubu Hospital and Ryukyu University Hospital. NTM lung disease, defined according to the American Thoracic Society criteria, was extracted and identified. Patient9s clinical background, and chest CT findings were compared between MAC (Mycobacterium avium complex) and RGM (rapid growing mycobacteria)infected patients. Results: One hundred and fourteen patients were diagnosed as NTM lung disease (MAC [n=38] and RGM [n=64]). Of these, eight patients were tracheotomized and were subsequently infected with RGM. No tracheotomized patients developed MAC (RGM 14.3%, MAC 0%, p=0.0232). Bronchiectasis on CT was observed more frequently in MAC group(78.9%) than inRGM group (43.8%) (p=0.0004). Nodular lesions were also frequently seen inMAC group than in RGM group (63.2% vs 29.7%; p=0.0002). Conclusion: In comparison to the reports from mainland Japan, RGM was more frequently isolated in Okinawa. A recent study showed that cystic fibrosis, gastroesophageal disease, and previous mycobacterial lung disease were risk factors for developing RGM lung disease. Although further studies are needed, tracheostomy might be another possible risk factor to cause RGM induced NTM lung disease.