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Trends in antituberculosis drug resistance in Karonga District, Malawi, 1986-1998
D K Warndorff1, M Yates, B Ngwira
1Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, UK.
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, isoniazid, rifampicin or ethambutol) was 9.6%, and to isoniazid 7.2%. Initial resistance to at least isoniazid and rifampicin (multidrug resistance) was seen in only six patients. No initial resistance to ethambutol was found. There 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 or human immunodeficiency virus (HIV) status and initial or acquired drug resistance.
Conclusions:
Changes in acquired resistance may reflect the recent performance of a control programme more quickly than those in initial resistance. It is encouraging that acquired resistance decreased and levels of multidrug resistance were low despite more than a decade of use of rifampicin. The lack of association between HIV and drug resistance confirms findings elsewhere in Africa.