The frequency of isolation of non-tuberculous mycobacteria (NTM) species from respiratory specimens is increasing, however the clinical relevance of such identifications vary by mycobacterial species and geographical location. A retrospective study of 853 NTM isolates from respiratory samples from 386 patients over seven years was performed. Clinical records and radiographic information were examined. Clinical significance was assessed by American Thoracic Society diagnostic criteria. 25% of all patients with respiratory isolates met criteria for non-tuberculous mycobacterial pulmonary disease (NTM-PD). Significant symptoms were weight loss, fever, night sweats, productive cough and haemoptysis. HIV co-infection was a significant risk factor for disease. Cavities, nodules and tree-in-bud were significant radiographic findings. Mycobacterium avium complex (MAC) were the dominant species isolated from this patient cohort. Mycobacterium abscessus (M. abscessus) was the species most likely to cause clinically significant disease and be sputum smear positive, thus warranting particular attention.

BackgroundThe frequency of clinical isolation of non-tuberculous mycobacteria (NTM) from the respiratory tract is increasing. American Thoracic Society (ATS) criteria aid the identification of clinically relevant isolates causing lung disease.Objectives(1) to audit diagnostic criteria used when treating NTM at our hospital (2) to identify the most clinically relevant isolates in our region and (3) to identify relevant associated patient demographics and radiological featuresMethodsrecords of all patients from whom NTM were isolated from respiratory samples between 2007 and 2014 were reviewed. Microbiological results, radiological findings and symptoms were reviewed to assess adherence to ATS diagnostic criteria and outcomes.ResultsNTM were isolated 826 times in 444 clinical episodes during the study period. Of 92 treated episodes, 81 (88%) met diagnostic criteria. If isolated, M. abscessus was most likely to be clinically relevant [Figure 1] and sputum smear positive. Isolation of M. kansasii and M. malmoense also warrant particular attention. Of the cases meeting ATS diagnostic criteria, the most common symptoms were fever, night sweats and weight loss. Concomitant oral steroid use and HIV positive status were common in this group. Cavitation and tree-in-bud were the most common CT radiographic appearances.Discussion21% of all clinical episodes with NTM isolation were treated for NTM disease. 88% of cases met ATS diagnostic criteria suggesting good adherence to guidance.ReferenceGriffith DE, et al. An Official ATS/IDSA Statement: Diagnosis, Treatment, and Prevention of Nontuberculous Mycobacterial Diseases. Am J Respir Crit Care Med 2007;175:367–416.Abstract S41 Figure 1Cliniacl relevance of Pulmanary NTM isolates