Tuberc Respir Dis.  1975 Dec;22(4):151-157. 10.4046/trd.1975.22.4.151.

The Criteria of Drug Resistance to Secondary Antituberculosis Drugs

• KMID: 2528978
• DOI: http://doi.org/10.4046/trd.1975.22.4.151

Abstract

A retrospective investigation was made to set criteria of drug resistance to so-called secondary antituberculosis drugs, namely, rifampicin, ethambutol, ethionamide, prothionamide, cycloserine and kanamycin. Youman’ s liquid medium was used for sensitivity testing. The strains were divided into four groups: Wild strains; pretreatment strains to each examining drug; probably sensitive strains (the last strains from the patients who have attained negative conversion subsequently); and probably resistant strains (the strains from the patients who have failed to more than six months of chemotherapy). The numbers of strains tested were as following s‘ 406 strains for rifampicin; 798 strains for ethambutol; 786 strains for ethionamide; 576 strains for prothionamide; 1, 182 strain s for cycloserine; 431 strains for kanamycin respectively. The distributions of inhibitory concentrations of each drug were compared. Attempts were made to classify resistance according to the pealk value of difference between the cumulative distribution of inhibitory concentrations, and as far as possible, to include smallest number of wild, pretreatment or probably sensitive strains and the greatest number of probably resistant cultures as resistant, The results showed that the growth on following concentrations could be classified as resistant: rifampicin in 0.4 mcg/ ml; ethambutol 3. Omcg/ ml; ethionamide 3. 2mcg/ ml ; prothionamide 0.3 mcg/m1. ; cycloserine 10 mcg/ m1; and kanamycin 0.8 mcg/ m1. respectively,