Macrophage Virulence Assays

Mycobacterium tuberculosis is a facultative intracellular pathogen, which can survive and replicate within the host macrophage. It is transmitted via the aerosol route, which delivers the bacillus to the alveolus of the lungs. The initial phase of granuloma formation within the lung requires that the bacterium is ingested by alveolar macrophages. Intracellular replication begins and an inflammatory reaction, involving recruitment of mononuclear leukocytes to the site, is initiated. The resultant accumulation of mononuclear leukocytes (mono-cytes, macrophages, and lymphocytes) is known as a granuloma. The growth of the mycobacteria at this stage in the infection is largely intracellular and acid fast bacilli can be visualized within the macrophages of the granuloma (1 ).