In vitro activity of rifampicin, rifapentine and rifabutin against South Indian isolates of Mycobacterium tuberculosis.

Venkataraman, P.; Paramasivan, C.N.; Prabhakar, R.

Indian Journal of Tuberculosis; 1993; 40; 17-20.

M. tuberculosis isolates from 51 resistant and 52 susceptible to Rifampicin patients were concurrently tested for in vitro susceptibility to Rifampicin, Rifapentine and Rifabutin. All the 52 Rifampicin susceptible strains were susceptible to Rifapentine, the geometric mean MICs being 13.3 m g/ml for Rifampicin and 6.0 m g/ml for Rifapentine. However, the geometric mean MIC for Rifabautin was as low as 13 m g/ml.

         All 51 Rifampicin resistant strains were also resistant to Rifapentine, indicating a complete cross-resistance between the two compounds. However, 11 (22%) of the Rifampicin resistant strains were found to be susceptible to Rifabutin. The geometric mean; MICs of the 40 resistant strains were 22 m g/ml for Rifampicin and113 m g/ml for Rifabutin. Thus, even among Rifampicin resistant strains, Rifabutin showed a 1.97 fold higher activity; the difference in the means attained statistical significance.

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