CORRELATION OF MOLECULAR RESISTANCE MECHANISMS AND PHENOTYPIC RESISTANCE LEVELS IN STREPTOMYCIN-RESISTANT MYCOBACTERIUM-TUBERCULOSIS

Quantitative susceptibility testing of clinical isolates of streptomyc in-resistant Mycobacterium tuberculosis demonstrated that there is a c lose correlation between the molecular resistance mechanism and the in vitro activity of streptomycin: mutations in rpsL were mainly associa ted with high-level resistance, mutations in rrs were associated with an intermediate level of resistance, and streptomycin-resistant isolat es with wild-type rpsL and rrs exhibited a low-level resistance phenot ype. Investigations of streptomycin-resistant isolates with wild-type rpsL and rrs revealed that (i) there is no cross-resistance to other d rugs and (ii) a permeability barrier may contribute to resistance, bec ause resistance was significantly lowered in the presence of a membran e-active agent.