Frequency and clinical significance of respiratory isolates of non-tuberculous mycobacteria in Riyadh, Saudi Arabia.

Background And Aims: The prevalence of pulmonary non-tuberculous mycobacteria (NTM) disease is increasing worldwide. The aim of this study was to assess the frequency and clinical significance of NTM isolated from respiratory specimens at King Abdul-Aziz Medical City-Riyadh, Saudi Arabia.

Methods: The medical records of all patients who had at least one respiratory specimen that was positive for growth of NTM between 2006 and 2012 were retrospectively reviewed. The clinical significance of the isolates was determined using the diagnostic criteria for NTM disease published by the American Thoracic Society (ATS).

Result: A total of 380 respiratory specimens with positive culture for NTM from 142 patients were identified. Forty patients (28%) had definite pulmonary NTM disease with a mean (± standard deviation) age of 54 ± 16 years, 58% were male and 50% had had underlying chronic lung disease. Mycobacterium avium complex (MAC) (n = 19, 48%) and Mycobacterium abscessus (n = 10, 25%) were the most commonly encountered NTM. The clinical manifestations of NTM lung disease are non-specific, with symptoms indistinguishable from pulmonary tuberculosis (TB). The most common radiological features of NTM lung disease were nodular bronchiectasis (45%) and fibrocavitary lesions (40%).

Conclusions: Twenty-eight percent of the patients with NTM isolates met the ATS diagnostic criteria for NTM lung disease. MAC and M. abscessus were the most encountered NTM isolated species that caused NTM lung disease in our population, which is a rate similar to many previous studies.