Nontuberculous Mycobacteria Isolated from Respiratory Specimens during Recent Two Years: Distribution and Clinical Significance

Lee, Min Kyoung; Seo, Yiel Hea; Jeong, Ji Hoon; Park, Pil Whan; Kim, Kyung Hee; Ahn, Jeong Yeal; Kim, Jin Yong; Park, Jeong Woong

Abstract

BACKGROUND
The isolation of nontuberculous mycobacteria (NTM) has been increasing worldwide as well as its clinical importance. The aim of this study was to investigate the distribution and clinical significance of NTM that has been isolated from respiratory specimens during a recent two-year period at a tertiary hospital.
METHODS
We analyzed respiratory samples that were obtained between January 2009 and December 2010 for AFB culture. We retrospectively reviewed the electronic medical records of these patients to obtain both clinical and radiologic information. NTM pulmonary disease was defined by using the guidelines provided by the America Thoracic Society/Infectious Diseases Society of America.
RESULTS
Among the 1,601 specimens that resulted in a positive AFB culture, 310 (19.4%) were NTM. In 189 patients, the most common isolate was M. avium-intracellulare complex (MAC) (127, 67.2%), which was then followed by M. abscessus (31, 16.4%), M. fortuitum (10, 5.3%), M. kansasii (9, 4.8%), and other NTM species. Of these, 93 (49.2%) patients were diagnosed with NTM pulmonary disease. MAC, M. abscessus, and M. kansasii were more virulent than the other species. None of the cases of NTM pulmonary disease were caused by M. fortuitum, M. chelonae, M. peregrinum, M. terrae complex, or M. gordonae.
CONCLUSION
In Korea, the prevalence of NTM isolates is increasing, as are the cases of pulmonary disease. The pathogenic potential of NTM differs enormously by species and as a result the treatment of NTM lung disease depends on which species has caused the infection. The isolation and identification of NTM isolated from respiratory specimens are mandatory in order for clinical microbiology laboratories to make an accurate diagnosis and suggest the proper treatment of the NTM disease.