Frequency and clinical significance of respiratory isolates of non-tuberculous mycobacteria in Riyadh, Saudi Arabia Abdullah AL-Harbi 1 , Hamdan AL-Jahdali 1 , Sameera AL-Johani 2 , Salim Baharoon 3 , Salih Bin Salih 4 and Mohammad Khan 1 1 Department of Medicine, Pulmonary Division, King Abdulaziz Medical City, King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia 2 Department of Pathology and Laboratory Medicine, King Abdulaziz Medical City, King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia 3 Department of Critical Care, King Abdulaziz Medical City, King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia 4 Department of Medicine, King Abdulaziz Medical City, King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia Abstract 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 bron- chiectasis (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 popula- tion, which is a rate similar to many previous studies. Please cite this paper as: AL-Harbi A, AL-Jahdali H, AL-Johani S, Baharoon S, Bin Salih S and Khan M. Frequency and clinical significance of respiratory isolates of non-tuberculous mycobacteria in Riyadh, Saudi Arabia. Clin Respir J 2014; ••: ••–••. DOI:10.1111/crj.12202. Key words clinical significance – features of NTM lung disease – Mycobacterium avium complex – non-tuberculous mycobacteria – pulmonary NTM disease Correspondence Abdullah AL-Harbi, MBChB, FRCPC, Department of Medicine, Pulmonary Division; King Abdulaziz Medical City, P.O. Box 22490, MC 1443, 11426 Riyadh, Saudi Arabia. Tel: (900) 8011111 #17595 Fax: (966) 8011111 #14229 email: harbia7@ngha.med.sa Received: 20 April 2014 Accepted: 01 August 2014 DOI:10.1111/crj.12202 Authorship and contributorship Principal author, A.A. performed the research, collected and analyzed the data, and wrote the manuscript. All the other authors contributed to the design of the study, the interpretation of results, and the revision of the manuscript. Ethics The study was approved by Institutional Review Board (IRB) of the National Guard Health Affairs (NGHA), Riyadh, Saudi Arabia. All data were anonymized and pooled for retrospective analysis. Conflict of interest The authors have stated explicitly that there are no conflicts of interest in connection with this article. Grants and financial support None. Abbreviations: ATS American Thoracic Society BAL bronchoalveolar lavage COPD chronic obstructive pulmonary disease CT computed tomography IDSA Infectious Disease Society of America MAC Mycobacterium avium complex NTM non-tuberculous mycobacteria TB tuberculosis The Clinical Respiratory Journal ORIGINAL ARTICLE 1 The Clinical Respiratory Journal (2014) • ISSN 1752-6981 © 2014 John Wiley & Sons Ltd Please cite this paper as: AL-Harbi A, AL-Jahdali H, AL-Johani S, Baharoon S, Bin Salih S and Khan M. Frequency and clinical significance of respiratory isolates of non-tuberculous mycobacteria in Riyadh, Saudi Arabia. Clin Respir J 2016; 10: 198–203. DOI:10.1111/crj.12202. The Clinical Respiratory Journal (2016) • ISSN 1752-6981 V C 2014 John Wiley & Sons Ltd 198