Mycobacterium abscessus (MA) has an increasing prevalence in CF lung and a large diversity in its clinical presentation. The hypothesis is that the strains of MA from patients with deteriorated lung functionality may differ in pathogenicity from the ones isolated from asymptomatic patients. The aims of the project are 1) to detect genomic differences correlated to different clinical phenotype; 2) to investigate the pathogenicity of MA sspp by single-cell infection model and by a murine model of infection. These assays have the potential of differentiating the two types of organisms and in this way to identify the patients who could benefit from antimicrobial treatment.