Identification of a genomic fragment of Mycobacterium tuberculosis responsible for in vivo growth advantage.

The purpose of this work was to develop a system to identify virulence determinants of M. tuberculosis by genetic complementation. The ability to grow in mouse spleen and/or lung was defined as a potential phenotype for virulence. Enrichment for growing recombinant clones from a pool of H37Ra transformants containing the integrating pYUB178::H37Rv cosmid library was accomplished by in vivo selection. A molecular strategy was devised to isolate and clone the 25-kb H37Rv genomic fragment ivg that conferred in vivo growth advantage to H37Ra. This study is a first step toward understanding the genetics of virulence in M. tuberculosis. A detailed description of these experiments has been submitted for publication in Infection and Immunity.