[Clinical and microbiological features of patients with pulmonary nontuberculous mycobacterial infection]

The prevalence of pulmonary nontuberculous mycobacterial infection (pNTM) is currently increasing. Furthermore, its clinical feature is reported to be gradually changing. However, few reports to clarify the current features of pNTM have been published. The aim of this study is to investigate microbiological and clinical features of pNTM.

This study was a retrospective observational study. Patients with pNTM visited to Dokkyo Medical University Koshigaya Hospital between January 2009 and December 2010 were enrolled. All patients fulfilled the diagnostic criteria in Japanese guidelines for nontuberculous mycobacterial pulmonary disease published in 2008. Medical records were reviewed to obtain information about the enrolled patients.

Total 143 patients (49 males and 94 females, age 67 +/- 10 yrs) were enrolled in this study. Only 11.9% of patients had malignant diseases and 5.6% had diabetes mellitus whereas 79% had no comorbidity. Nearly 60% of patients showed normal BMI. At the time of diagnosis, 52.0% of patients had no symptom whereas 22.3% had cough and/or sputum, and 7.1% had hemoptysis. The results of smear examination with acid-fast staining were negative in 80.4%, +/- in 9.8%, 1 + in 7.7% and 2 + in 2.1%. Causative pathogens detected with acid-fast bacillus culture were Mycobacterium avium (M. avium) (74.8%), M. intracellulare (14.0%), M. fortuitum (3.5%), M. abscessus (2.8%), M. kansasii (2.8%) and others.

This study showed that majority of patients had no symptoms and/or negative results of smear examination with acid-fast staining. It is crucial to consider these facts when a diagnostic test of pNTM is performed.