Non-Tuberculous Mycobacteria: Seven-Year Experience of a Tertiary Hospital

Nuno Ferreira Monteiro, Susana Peres, Kamal Mansinho


Introduction: Non-tuberculous mycobacteria are ubiquitous organisms. Precise determination of infection numbers is difficult, since reporting them to public health departments is frequently not mandatory; furthermore, isolating a non-tuberculous mycobacteria does not necessarily translate into disease. The aims of this study were to ascertain non-tuberculous mycobacteria data of a tertiary hospital, determine the incidence and approach to colonization versus disease, and the incidence of predisposing comorbidities.
Material and Methods: Retrospective study in a tertiary hospital, involving patients with positive cultural exam for non-tuberculous mycobacteria in any biological sample, from 2010 to 2017.
Results: A total of 125 non-tuberculous mycobacteria isolates was identified, corresponding to 96 patients. Of these, 57.4% were male (n = 54); median age was 65 years (interquartile range = [50 - 82]). From these, 60.7% (n = 57) had some degree of immunosuppression, most frequently due to malignant tumour (49.0%) or HIV infection (39.2%). It was found that 29 patients (31.0%) had structural respiratory tract changes. Colonization was defined in 65.6% of patients (n = 63). While 71.0% of non-tuberculous mycobacteria infections were pulmonary, the remaining 29.0% presented as disseminated. According to available clinical records, 60.6% (n = 20) of the presumably infected patients fulfilled American Thoracic Society diagnostic criteria for non-tuberculous mycobacteria disease.
Discussion: Several cases of non-tuberculous mycobacteria infection in this study presented as life-threatening, multi-systemic disease, highlighting the importance of accurate diagnosis and timely treatment. Other cases of presumed infection might instead have corresponded to colonization, possibly resulting in futile therapy.
Conclusion: While there are diagnostic criteria for treatment of non-tuberculous mycobacteria infections, no such guidelines exist to assess colonization. One of the most challenging aspects remains the correct differentiation between colonization and early-stage infection.


Mycobacterium Infections, Nontuberculous/epidemiology; Nontuberculous Mycobacteria; Portugal

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