In cystic fibrosis patients, the presence of Mycobacterium abscessus (M.a.) in the lungs is related to a broad spectrum of clinical features, ranging from asymptomatic to severe pulmonary disease. Researchers hypothesized that the strains of M.a. isolated in patients with deteriorated lung functionality may differ in pathogenicity from the ones isolated in asymptomatic patients. To this aim M.a. strains coming from patients with different respiratory symptoms have been selected within a large number of fully characterized by whole genome sequencing (WGS) M.a. bacteria (project FFC#13/2016). The selected strains belonging to three subspecies (M. abscessus, M. bolletii and M. massiliense) will be used to infect a new mouse model, where to investigate if different genomes and virulence markers are present, and are related to the different clinical picture. Detection of different pathogenic activity in the three M.a. sspp and, in case, the identification of hypervirulent circulating strains would permit the differentiation of M.a. infections and patients requiring, or not requiring, pharmacologic treatment.