Pathophysiology: Multi-drug-resistant tuberculosis (MDR-TB) is defined as a form of TB infection caused by bacteria that are resistant to treatment with at least two of the most powerful first-line anti-TB drugs, isoniazid (INH) and rifampicin. MDR-TB infection may be classified as either primary or acquired. MDR-TB can become resistant to the major second-line drug groups: fluoroquinolones and injectable drugs.
Statistics: TB is the world's leading cause of death from a single infectious organism, killing 2 million people each year. The TB crisis has intensified because multidrug-resistant (MDR) microbes have emerged. An incurable form of the disease may develop from infections caused by these organisms. 81 deaths in Canada 2000 (Regional Core Health Data Initiative, Pan American Health Organisation, 2003).
Treatment: The treatment and prognosis of MDR-TB are much more akin to those for cancer than to those for infectionTreatment of MDR-TB requires treatment with second-line drugs, usually four or more anti-TB drugs for a minimum of 6 months, and possibly extending for 18–24 months if rifampin resistance has been identified in the specific strain of TB with which the patient has been infected.
Major Research: The identification of genes that play a role in the virulence of the bacilli, either in vitro or in vivo. Structural genes and regulators were discovered. Their functions are being studied. A loci involved in the interaction of the TB bacilli with phagocytes is located on horizontally transferred element. This opened the way to the study of horizontal transfer in M. tuberculosis project. Horizontal transfer Mutant strains with an inactivation of the phoP/phoR two component regulatory system were shown to be attenuated and constitute promising vaccine candidate under clinical trials.