Abstract
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.
Highlights
The frequency of nontuberculous mycobacteria (NTM) isolation from respiratory samples and non-tuberculous mycobacteria (NTM) pulmonary disease (NTM-PD) is increasing in the UK1,2 and many other countries worldwide[3,4]
From 2007 to 2014 there were 853 NTM isolates from 386 patients in respiratory specimens at Queen Alexandra Hospital, Portsmouth, UK. 88% (748 of 853) NTM isolates were from sputum culture, 12% (104 of 853) were from broncho-alveolar lavage (BAL) and one sample was a lung swab
This differs from observations in other non-coastal UK cities, for example previous retrospective studies in London showed that Mycobacterium kansasii (M. kansasii) or Mycobacterium xenopi (M. xenopi) were the dominant organisms[12,13]
Summary
The frequency of nontuberculous mycobacteria (NTM) isolation from respiratory samples and NTM pulmonary disease (NTM-PD) is increasing in the UK1,2 and many other countries worldwide[3,4]. In part this is explainable by improved laboratory methods and increasing clinician awareness, it is widely accepted to represent a true increase in disease incidence[5]. NTM species differ in their pathogenicity, with a higher propensity to cause disease in patients with impaired immunity This can be either locally impaired immunity due to pre-existing lung disease or systemic, such as with haematological malignancy, immunosuppressive treatment or HIV/AIDS7.
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