title: Frequency and clinical significance of respiratory isolates of non-tuberculous mycobacteria in Riyadh, Saudi Arabia.
abstract: OBJECTIVE
  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).
  
  
  RESULTS
  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.
authors.affiliation: Department of Medicine, Pulmonary Division, King Abdulaziz Medical City, King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia.
authors.forename: Abdullah
authors.initials: A
authors.lastname: Al-Harbi
authors.affiliation: Department of Medicine, Pulmonary Division, King Abdulaziz Medical City, King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia.
authors.forename: Hamdan
authors.initials: H
authors.lastname: Al-Jahdali
authors.affiliation: Department of Pathology and Laboratory Medicine, King Abdulaziz Medical City, King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia.
authors.forename: Sameera
authors.initials: S
authors.lastname: Al-Johani
authors.affiliation: Department of Critical Care, King Abdulaziz Medical City, King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia.
authors.forename: Salim
authors.initials: S
authors.lastname: Baharoon
authors.affiliation: Department of Medicine, King Abdulaziz Medical City, King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia.
authors.forename: Salih
authors.initials: S
authors.lastname: Bin Salih
authors.affiliation: Department of Medicine, Pulmonary Division, King Abdulaziz Medical City, King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Khan
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008171:Lung Diseases / Q000453:epidemiology* / Q000382:microbiology* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009165:Mycobacterium Infections, Nontuberculous / Q000453:epidemiology* / Q000382:microbiology* / Q000473:pathology; D015269:Mycobacterium avium Complex / Q000302:isolation & purification; D009170:Nontuberculous Mycobacteria / Q000145:classification* / Q000302:isolation & purification*; D015995:Prevalence; D012189:Retrospective Studies; D012529:Saudi Arabia / Q000453:epidemiology
keywords: Mycobacterium avium complex; clinical significance; features of NTM lung disease; non-tuberculous mycobacteria - pulmonary NTM disease