[Characterization of the drug resistance spectrum of rifampicin-resistant M. tuberculosis to other first-line antituberculous drugs].

The spectrum of drug-resistance of rifampicin-resistant M. tuberculosis strains to other first-line antituberculous drugs was studied. Streptomycin resistance was found to be prevalent in the structure of monoresistance. Resistance to two agents--isoniazid and streptomycin--was more common in the structure of polyresistance; that to a combination of isoniazid, rifampicin, and streptomycin was seen in the structure of multidrug resistance. The rifampicin-resistant strains were also resistance to isoniazid and streptomycin in 95.1 and 98.7% of cases, respectively. Resistance to isoniazid, streptomycin, and ethambutol occurs more frequently when cytosine is substituted for thymidine (TCG-->TTG) in codon 513 of the rpoB gene.