Trends in antituberculosis drug resistance in Karonga District, Malawi, 1986-1998

SETTING: Karonga District, Malawi. OBJECTIVES: TO examine long term trends in initial and acquired resistance to antituberculosis drugs in a rural area of Africa. DESIGN: Monitoring of all patients with culture-confirmed tuberculosis 1986 -1998. RESULTS: Initial drug resistance results were available for 1121 patients. The proportion resistant to any of the first line drugs (streptomycin, ison iazid, rifampicin or ethambutol) was 9.6%, and to isoniazid 7.2%. Initial r esistance to at least isoniazid and rifampicin (multidrug resistance) was s een in only six patients. No initial resistance to ethambutol was found. Th ere was no significant change in initial drug resistance over time. Overall , 22/120 (18%) patients with previous treatment were resistant to at least one drug; only one had multidrug resistance. Acquired resistance decreased over the period of the study. There were no associations between age, sex o r human immunodeficiency virus (HIV) status and initial or acquired drug re sistance. CONCLUSIONS: Changes in acquired resistance may reflect the recent performa nce of a control programme more quickly than those in initial resistance. I t is encouraging that acquired resistance decreased and levels of multidrug resistance were low despite more than a decade of use of rifampicin. The l ack of association between HIV and drug resistance confirms findings elsewh ere in Africa.