Progression and Treatment Outcomes of Lung Disease Caused by Mycobacterium abscessus and Mycobacterium massiliense

Abstract

Introduction: Mycobacterium abscessus and Mycobacterium massiliense are grouped as the Mycobacterium abscessus complex. Although M. massiliense lung diseases are reported to have better treatment response than M. abscessus lung diseases, clinical comparisons between these two species remain limited. The aim of this study was to elucidate the differences between M. abscessus lung diseases and M. massiliense lung diseases in terms of progression rate, treatment outcomes, and the predictors thereof.

Methods: Between January 1, 2006 and June 30, 2015, 56 patients and 54 patients were diagnosed with M. abscessus and M. massiliense lung diseases, respectively. The time to progression requiring treatment and treatment outcomes were compared between the two groups of patients, and predictors of progression and sustained culture conversion with treatment were analyzed. In addition, mediation analysis was performed to evaluate the effect of susceptibility to clarithromycin on treatment outcomes.

Results: During follow-up, 21 of 56 patients with M. abscessus lung diseases and 21 of 54 patients with M. massiliense lung diseases progressed requiring treatment. No difference was detected in the time to progression between the two patient groups. Lower body mass index, bilateral lung involvement, and fibrocavitary type disease were identified as predictors of disease progression. Among the patients who began treatment, infection with M. massiliense rather than M. abscessus and the use of azithromycin rather than clarithromycin were associated with sustained culture conversion, while lower body mass index was a negative predictive factor. The difference in treatment outcomes between these two species was partly mediated by the organisms susceptibility to clarithromycin.

Conclusions: Progression rates were similar but treatment outcomes differed significantly between patients with lung disease caused by M. abscessus and M. massiliense. This difference in treatment outcomes was partly explained by the susceptibility of these organisms to clarithromycin.