Identification of Non-Tuberculous Mycobacteria in COPD Patients Undergoing Lung Volume Reduction: More Frequent than Expected?

The group of non-tuberculous mycobacteria (NTM) – also referred to as environmental mycobacteria – includes more than 150 species of the genus Mycobacterium distinct from the Mycobacterium tuberculosis complex. A limited number of these intracellular acid-fast bacilli may be pathogenic for humans and cause a necrotizing granulomatous inflammation. The most frequent clinical manifestations of NTM are lung infections, adenitis, skin infections, and bacteremia in immunosuppressed hosts. Not all species are pathogenic in humans and the risk of developing a clinical disease depends on the equilibrium between the pathogenicity of the strain and host characteristics (e.g., immunosuppression, comorbidities).Over the last decades, there has been an increasing awareness of NTM infections in the medical community. Epidemiological data in the US, Europe, and other parts of the world show an increase in prevalence and incidence of NTM isolation [1]. The association between certain respiratory disorders and NTM is well known, but specific data regarding the clinical and prognostic impact of identifying NTM in COPD patients are scarce [2]. In COPD, NTM may be associated with a higher incidence of acute exacerbations and a more rapid deterioration of pulmonary function [3].The development of endoscopic lung volume reduction (ELVR) in severe COPD has led to invasive bacterial sampling in patients who would have been otherwise unlikely to undergo bronchoscopy. It is standard procedure in our center to perform systematic cultures for mycobacteria from bronchial aspirates collected during every bronchoscopy.We report a series of 44 patients with severe COPD who underwent ELVR between October 2013 and October 2017 at our hospital, from which we retrospectively collected bacteriological findings from all bronchial aspirates obtained during the procedure.All patients included met the eligibility criteria for ELVR, namely: emphysema, persisting dyspnea despite maximal medical therapy including recent rehabilitation, age <75 years, being an ex-smoker for >6 months, FEV1 <45% of predicted, marked hyperinflation (residual volume >175% of predicted), 6-min walking distance >140 m, and no or few acute exacerbations during the year prior to the procedure. In all patients, chest computed tomography (CT) showed severe emphysema. Only one patient, who previously underwent a single lung transplant a few years ago, was immunosuppressed.NTMs were isolated in 8/44 patients (18.2% of cases) (Table 1). Mycobacterium avium complex was the most prevalent NTM identified (5/8, all M. avium subtype). Other NTM identified were: Mycobacterium xenopi (n = 1), Mycobacterium gordonae (n = 1) and a rapidly growing NTM (n = 1; rapidly growing, non-pigmented).At the time of ELVR, none of the patients had images suggestive of NTM infection on CT scans. From 8 patients with NTM isolation, only 4 had an opacity or nodule on the CT. Interestingly, no patient with NTM isolation had bronchiectasis.None of the samples were microscopy positive. NTM were isolated once in most patients (6/8), twice in one, and three times in another. Of the 8 patients with NTM isolation, two had a single bronchoscopy, three had 2 bronchoscopies, two had 3 bronchoscopies, and one had 4. With a mean follow-up of 993 days (range: 420–1,566), no patient required specific antimycobacterial treatment for NTM-associated lung disease, according to ATS/ERS criteria [4].Other pathogens isolated from bronchial aspirates were Haemophilius influenzae (4/44 patients), various gram-negative bacilli (11/44 patients), and Aspergillus species (6/44 patients).The rate of NTM colonization in our cohort is significantly higher than previously reported in such a population. Moreover, this rate is significantly higher than the overall NTM identification rate we have in our global bronchoscopy population in our center, which is 6% (22 bronchial aspirates out of 358, p = 0.01, t test). This suggests that these patients are particularly susceptible to colonization when exposed and may therefore be at higher risk of developing active NTM infection. In this retrospective study, however, with an average follow-up period of approximately 3 years, no patient developed an active NTM disease.We found no difference between patients with or without NTM colonization in terms of severity of obstruction, use of steroids (oral or inhaled), or any other cause of immunosuppression. Given the retrospective design of this report and the small number of patients, we are unable to assess the clinical impact of NTM identification on lung function and disease progression. However, the frequent colonization by NTM in severe COPD suggests that NTM infection may be underestimated in this population. The clinical impact of this finding has to be further explored by larger prospective studies, but it seems reasonable to recommend a systematic search for NTM in COPD patients before initiating immunomodulatory macrolide treatments, in frequent exacerbators, and in presence of a rapid decline of FEV1.Geneva University Hospitals.Nothing to disclose.No external funding.