Primary and acquired drug resistance in adult black patients with tuberculosis in South Africa: results of a continuous national drug resistance surveillance programme involvement.

Drug resistance is a major problem in the treatment of tuberculosis, and monitoring programmes are essential in control of this disease. The extent of primary resistance in a community is an important indication of the effectiveness of treatment schedules. Since 1965 the Tuberculosis Research Institute (TBRI) of the South African Medical Research Council has performed 25 annual surveys of drug resistance in adult black tuberculosis patients where the disease is most prevalent. Methodology for patient selection, specimen collection, laboratory procedures and criteria for drug resistance were strictly adhered to. All specimens were processed in a central laboratory supervised by the same two technologists. Between 1965 and 1988 a total of 33,111 strains of Mycobacterium tuberculosis were isolated from new cases and 19,134 from old cases. Both primary and acquired resistance to the 5 major antituberculosis drugs has decreased dramatically. Sex and age do not influence resistance rates, while patients' ethnic origin and geographical location do. The results indicate that current tuberculosis treatment practices are satisfactory. The prevalence of primary drug resistance in black South Africans is now intermediate between those countries where eradication of tuberculosis is well advanced and those where the disease remains a public health problem. Also, it can be shown that comparable and clinically significant data can be obtained from a central laboratory employing unsophisticated and inexpensive drug susceptibility testing procedures.