RIFAMPIN-RESISTANT MYCOBACTERIUM-KANSASII

We identified 36 rifampin-resistant Mycobacterium kansasii isolates, i ncluding 17 (4%) of 464 isolates recovered in Texas between 1989 and 1 992. Of 29 patients infected with rifampin-resistant M. kansasii whose history of medication was known, 90% had previously received rifampin , and 58% of these patients had been treated with one or two effective drugs. Thirty-two percent of rifampin-resistant isolates recovered si nce 1989 were from patients who were seropositive for human immunodefi ciency virus (HIV) infection. Twenty courses of therapy with a four-dr ug regimen determined on the basis of in vitro susceptibilities were a dministered to 16 patients from whom rifampin-resistant isolates were recovered; the therapy did not include surgery. Sputum cultures conver ted to negative as the result of 90% of treatments (time to conversion : mean, 11 weeks; range, 4-20 weeks). Bacteriologic relapses occurred in four of five patients who withdrew from therapy after being culture negative for less than or equal to 6 months of therapy and in one of 12 patients who were culture negative for at least 12 months of therap y (mean, 16.3 months). This study suggests that the prognosis for cure of infection due to rifampin-resistant M. kansasii with chemotherapy alone is excellent, although the number of cases appears to be increas ing, in part because of the HIV disease epidemic.