Introduction: Pulmonary diseases caused by non-tuberculous mycobacteria have a lower incidence than those caused by Mycobacterium tuberculosis but are no less worrying.
Fundamental for recovering is to obtain the microbiological negativization of the sputum culture test for the search for atypical mycobacteriosis1. Epidemiology appears to play an important role in patient outcome1. Aims. The aim of this study is to identify potential predictive factors for microbiological negation. Methods.  We conducted a retrospective longitudinal study enrolling 14 outpatients with non-tuberculous mycobacterial disease at the respiratory department of Venere di Bari hospital. They were collected during the follow up period, anamnestic data on the pathogen, symptomatology and diagnostic timing. The study population was divided based on microbiological negativity into two subgroups that were compared for the study parameters by univariate and multivariate COX analysis. Results: Group 0 (no negativization, n = 5) had a median duration of symptoms before starting treatment of 29 weeks (10.5 - 34) compared to a median duration of 6 weeks (4 - 11) in group 1 (presence of negativization, n = 9). This finding is statistically significant and is confirmed by Cox survival analysis. Conclusions: Diagnostic delay is the main negative prognostic factor for microbiological negativity in patients with non-tuberculous mycobacteriosis, hence the crucial importance of early diagnosis.

Daley CL et Al. Treatment of nontuberculous mycobacterial pulmonary disease: an official ATS/ERS/ESCMID/IDSA clinical practice guideline. Eur Respir J. 2020 Jul 7;56(1):2000535.