Multidrug resistance in the world: the present situation

Tuberculosis (TB) is the leading cause of death attributable to a single infectious pathogen with one-third of the world population infected. In the USA, TB rates have fallen 3 years in succession after a sustained rise since 1985. More important are the multidrug-resistant tuberculosis (MDR-TB) cases, which are thought to be largely due to the breakdown in the delivery of health care in the USA in conjunction with HIV infection. In countries facing the HIV epidemic, the overlap of these two populations leads to a rapid acceleration of active TB and the emergence of MDR-TB. In the USA the most recent published survey (1991) revealed that 3.5% of strains were resistant to isoniazid and rifampin. Worldwide, MDR-TB is also thought to be highly prevalent, not only because of a breakdown in health infrastructure but also because of inappropriate prescription, lack of drug availability and the use of combination capsules in which the drugs are not bioavailable. Key points in therapy are to order susceptibility tests, obtain a complete drug history, treat with an adequate number of effective drugs and never, ever add a single drug to a failing regimen.