PATTERNS OF INITIAL AND ACQUIRED ANTITUBERCULOSIS DRUG-RESISTANCE IN KARONGA DISTRICT, MALAWI

There is concern that drug-resistant tuberculosis is increasing and ma y be concentrated among HIV-positive patients. Little information is a vailable from developing countries, where surveillance studies are oft en unable to distinguish resistance in previously untreated patients ( initial resistance) from resistance acquired following drug therapy, a nd where information on the HIV status of the patients is rare. Initia l resistance patterns reflect the strains being transmitted in the com munity. We have studied patterns of resistance in northern Malawi, whe re the Lepra Evaluation Project has been collecting data on drug resis tance since 1986. Initial drug sensitivity results were available for 373 new cases of tuberculosis. Initial resistance to at least one drug was found in 44 of these patients (11.8%, 95% CI 8.5-15.1): 13 were r esistant to streptomycin alone, 13 to isoniazid alone, and 17 to more than one drug. Only 3 patients showed initial rifampicin resistance-1 in isolation, 1 in combination with streptomycin, and 1 with triple re sistance. Drug resistance was not related to age, sex, or HIV status o f the patient and there was no evidence of any increase over the perio d studied. There was no evidence of geographic clustering of the resis tant strains, or of any increased risk of resistant strains in househo lds with previous tuberculosis cases. Acquired resistance during follo w-up was found in 5 of 329 patients with documented initially fully se nsitive strains. 5 patients with initial resistance seemed to show rev ersion to sensitivity. The absence of an increase in drug resistance, despite an increase in tuberculosis cases over the period, is encourag ing for the control programme. It emphasises the need to collect infor mation from many areas before assuming that increases in antituberculo sis drug resistance are occurring worldwide.