Drug Resistance Assays for Mycobacterium tuberculosis

The introduction of antimicrobial therapy of tuberculosis during the second half of the last century was a turning point in the millennium-old history of this disease. However, the problem of drug resistance emerged, and with it, two levels of concern. First, such resistance not only poses a public health threat to successful control of TB epidemics, but it also complicates the approach to treatment of individual patients. In previous reviews we have addressed the history of research and evolution of views based on these studies regarding the usefulness of drug susceptibility testing (1, 2). Historically, most skepticism regarding the need for drug susceptibility testing was related to the period before introduction of rifampin (RMP) and pyrazinamide (PZA). It often referred to the inability of laboratories to provide test results rapidly enough for the information to be used to adjust treatment regimens in a timely manner. In 1990, the American Thoracic Society (ATS) and the CDC published the following statement, “Given the low prevalence of drug-resistant Mycobacterium tuberculosis (MTBC) in most parts of the United States, the cost of routine testing of all initial isolates is diffi cult to justify” (3).