Clinical relevance of pulmonary non-tuberculous mycobacterial isolates in three reference centres in Belgium: a multicentre retrospective analysis

Yannick Vande Weygaerde,Peter Bomans,Natalie Lorent,Jerina Boelens,Taeyang Chin,Nina Cardinaels,Eva Van Braeckel,Emmanuel André

doi:10.1186/s12879-019-4683-y

Abstract

Background/objectivesAssessing the clinical relevance of non-tuberculous mycobacteria (NTM) isolated from respiratory samples can be challenging. The epidemiology and pathogenicity of NTM species vary geographically. We aimed to outline the clinical relevance and associated radiological patterns of NTM species isolated in Belgium.MethodsWe performed a retrospective multicentre analysis of all patients identified from the laboratory database with > 1 respiratory sample growing NTM from January 2010 through December 2017. We collected clinical, radiological and microbiological data through medical record review and assessed clinical relevance according to ATS/IDSA criteria for NTM pulmonary disease (NTM-PD).ResultsOf the 384 unique patients, 60% were male, 56% had a smoking history and 61% had pre-existing lung disease. Mycobacterium avium complex (MAC), M. gordonae and M. xenopi were the most frequently isolated species: 53, 15 and 8% respectively. 43% of patients met ATS/IDSA criteria, of whom 28% presented with fibrocavitary disease. Weight loss, fever, nodular bronchiectatic and fibrocavitary lesions on chest CT, and a positive acid-fast bacilli (AFB) stain were significantly associated with NTM-PD. The species with the highest pathogenic potential were M. abscessus (11/12), M. malmoense (6/7) and M. intracellulare (41/64).ConclusionIn our study, MAC was the most commonly isolated NTM species, but M. abscessus and M. malmoense showed the highest probability of being clinically relevant. Clinical relevance varied not only by species but also by radiological findings on chest CT and AFB staining. Clinicians should consider these elements in their treatment decision making. Prospective data including clinical outcome are needed to provide more robust evidence.

Highlights

Non-tuberculous mycobacteria (NTM) are ubiquitous in the natural environment and household water systems [1, 2]
We aimed to outline the epidemiology of respiratory NTM isolates in our region, assess their clinical relevance according to the American Thoracic Society (ATS)/Infectious Diseases Society of America (IDSA) criteria and explore the possibility of an association between clinical relevance and the radiological pattern on chest CT
We noted an increase in the number of respiratory NTM isolates from 51 in 2010 to 75 new isolations in 2017, whereas the number of new cases of NTM pulmonary disease (NTM-PD) remained approximately stable during our study period

Summary

Introduction

Non-tuberculous mycobacteria (NTM) are ubiquitous in the natural environment and household water systems [1, 2]. Over 180 different species have been identified, but only 32 have been reported causing human or animal disease [3]. Lung infections (NTM related pulmonary disease or NTMPD) account for 90% of NTM related disease. Patients with pre-existing lung disease like chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), and non-CF bronchiectasis are predisposed [4,5,6,7,8]. To a lesser extent NTM can cause infections of skin, sinuses, lymph nodes, or even lead to disseminated disease in case of innate or acquired immunodeficiency [5, 9].

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