Expression of contact-dependent cytolytic activity by Mycobacterium tuberculosis and isolation of the genomic locus that encodes the activity.

We investigated the presence of cytolytic activity in the virulent H37Rv and attenuated H37Ra strains of Mycobacterium tuberculosis and in the vaccine strain Mycobacterium bovis BCG. The virulent strain H37Rv expressed > 3-fold more contact-dependent cytolytic activity than the attenuated strain H37Ra, and the vaccine strain M. bovis BCG did not produce cytolytic activity. We also isolated an approximately 3.2-kbp fragment of the M. tuberculosis H37Rv genome that was capable of inducing this contact-dependent hemolytic activity in a nonhemolytic strain of Escherichia coli.