Clinically relevant mutations in the PhoR sensor kinase of host-adapted Mycobacterium abscessus isolates impact response to acidic pH and virulence.

Difficult-to-treat pulmonary infections caused by nontuberculous mycobacteria of the Mycobacterium abscessus group have been steadily increasing in the USA and globally. Owing to the relatively recent recognition of M. abscessus as a human pathogen, basic and translational research to address critical gaps in diagnosis, treatment, and prevention of diseases caused by this microorganism has been lagging behind that of the better-known mycobacterial pathogen, Mycobacterium tuberculosis. To begin unraveling the molecular mechanisms of pathogenicity of M. abscessus, we here focus on the study of a two-component regulator known as PhoPR which we found to be under strong evolutionary pressure during human lung infection. We show that PhoPR is activated at acidic pH and serves to regulate a defined set of genes involved in host adaptation. Accordingly, clinical isolates from chronically infected human lungs tend to hyperactivate this regulator enabling M. abscessus to escape macrophage killing.