Nontuberculous mycobacterial lung infections in Ontario, Canada: clinical and microbiological characteristics

The aim of this study was to determine gender and clinical phenotype frequencies in pulmonary nontuberculous mycobacterial (NTM) infection and the frequency of disease in NTM isolates.

The study is a retrospective observational cohort study of two overlapping cohorts: population cohort and clinical cohort. Setting The study was conducted at the University Health Network and Ontario Mycobacteriology Laboratory in Toronto, Ontario, Canada.

The population cohort consisted of all patients with one or more pulmonary NTM isolates in Ontario in 2003. The clinical cohort consisted of all patients with one or more pulmonary NTM isolates at our hospital in 2002-2003. Interventions The study entailed the review of laboratory records and demographics (both cohorts) and detailed clinical records (clinical cohort).

In the population cohort (N = 1651), females comprised 48% overall and 51% with microbiological disease criteria. In the clinical cohort (N = 552), females comprised 48% overall and 55% with NTM disease. In the population cohort, 45% fulfilled microbiological disease criteria, and in the clinical cohort 46% of patients had disease. Patients with MAC isolates fulfilled microbiological disease criteria in 51% of population cohort cases and all disease criteria in 52% of clinical cohort cases. Women more commonly fulfilled microbiological disease criteria in the population cohort (51 vs. 45%, P = 0.02) and all disease criteria in the clinical cohort (53 vs. 40%, P = 0.03). Among clinical cohort patients, 26% (13 women, 44 men) had fibrocavitation, while 62% (101 women, 37 men) had nodular bronchiectasis.

Women comprised a small majority with disease. Nodular bronchiectasis in women was most common, but significant proportions of each gender with each radiographic type were observed. NTM isolation, particularly MAC, was frequently associated with disease.