Cutting edge: Mycobacterium tuberculosis but not nonvirulent mycobacteria inhibits IFN-β and AIM2 inflammasome-dependent IL-1β production via its ESX-1 secretion system.

Mycobacterium tuberculosis extracellular DNA gains access to the host cell cytosol via the ESX-1 secretion system. It is puzzling that this extracellular DNA of M. tuberculosis does not induce activation of the AIM2 inflammasome because AIM2 recognizes cytosolic DNA.

The non-pathogenic mycobacteria M. smegmatis and M. fortuitum induce rapid host cell apoptosis via a caspase-3 and TNF dependent pathway.

Background: The HIV pandemic raised the potential for facultative-pathogenic mycobacterial species like, Mycobacterium kansasii, to cause disseminating disease in humans with immune deficiencies. In contrast, non-pathogenic mycobacterial species, like M. smegmatis, are not known to cause disseminating disease even in immunocompromised individuals.

Evidence for pore formation in host cell membranes by ESX-1-secreted ESAT-6 and its role in Mycobacterium marinum escape from the vacuole.

The ESX-1 secretion system plays a critical role in the virulence of M. tuberculosis and M. marinum, but the precise molecular and cellular mechanisms are not clearly defined.