Mycobacteria: Leprosy, a Battle Turned; Tuberculosis, a Battle Raging; Paratuberculosis, a Battle Ignored

Abstract

This chapter addresses three mycobacterial organisms that have entirely different profiles: Mycobacterium leprae, Mycobacterium tuberculosis, and Mycobacterium avium subsp. Several trends continue to gravely threaten progress toward further global reductions in tuberculosis (TB). Of the 85 species within the genus Mycobacterium, members of the Mycobacterium tuberculosis complex have evolved as one of the preeminent pathogens of man. The clinical course of TB can be roughly divided into three phases: primary infection, latent TB, and chronic active TB. Additionally, for both M. leprae and M. tuberculosis, multiple-drug therapy (MDT) is usually considered obligatory, to prevent the emergence of resistant mycobacterial strains. The other two components of this chapter enunciate in detail that even with the most intensive MDT regimes, neither M. leprae nor M. tuberculosis is eradicated. A provocative study has reported that mycobacterial antigen activation of toll-like receptors 2 (TLR2) on monocytes from tuberculoid leprosy patients induced differentiation into cells bearing the dendritic cell-specific intercellular adhesion molecule grabbing nonintegrin MPH and CD1b+ DC. Biopsies of lepromatous lesions reveal acute inflammation, with focal infiltrates of polymorphs, superimposed upon the chronic inflammation and high mycobacterial load of lepromatous (LL-BL) leprosy. Initial comparisons of M. leprae’s genome with that of M. tuberculosis and more recently with those of other mycobacterial species have made it possible to assign potential gene function to many of M. leprae’s genes. Additionally, an appropriately designed potent vaccine should protect against many, if not all, drug-resistant mutants of the infectious agent, an inevitability in leprosy that cannot be minimized.