Mycobacterium Avium Complex (MAC) Lung Disease in Two Inner City Community Hospitals: Recognition, Prevalence, Co-Infection with Mycobacterium Tuberculosis (MTB) and Pulmonary Function (PF) Improvements After Treatment

INTRODUCTION: The purpose of this study was to separate MAC lung disease from colonization and to define indications for treatment. MATERIALS AND METHODOLOGY: Over 4 years, we evaluated patients who had positive MAC cultures, MAC infection and coinfection with MTB. In the first study, 42 immunocompetent patients with sputum or BAL culture positive only for MAC during a single year (2004) were reviewed. On clinical and radiographic review, they were classified as disease related to MAC, likely related to MAC or unrelated to MAC. In the second study, we reviewed all immunocompetent patients, during two years (2004-2005), whose respiratory secretions cultured both MTB and nontuberculous mycobacteria (NTM). In the last study, we evaluated pulmonary function (PF) in patients with MAC infection before and after therapy (2006- 2007). PF was evaluated in patients following ATS guidelines. RESULTS: Lung disease was related/likely related to MAC in 21 patients (50%) and not related in 21 (50%). In patients with MAC-related lung disease, the primary physician did not consider the diagnosis except when that physician was a pulmonologist. Half of those with MAC-related lung disease were smokers, white and US-born. There were 12 immunocompetent patients with MTB and NTM cultures. Eleven were non-white and all were foreign-born. Presentation and clinical course were consistent with MTB. All 8 patients with abnormal PF improved. CONCLUSIONS: The prevalence of MAC lung infection in two inner city hospitals was four times higher than that of TB. The indication for treatment of MAC infection should also rely heavily on clinical and radiological evidence when there is only one positive sputum culture. The diagnosis was considered only when the admitting physician was a pulmonologist. Most patients with combined infection were clinically consistent with MTB and responded to anti MTB treatment alone. Treatment with anti-MAC therapy improved PF in those patients whose PF was abnormal to begin with.