MOLECULAR ANALYSIS OF KANAMYCIN AND VIOMYCIN RESISTANCE IN MYCOBACTERIUM-SMEGMATIS BY USE OF THE CONJUGATION SYSTEM

We examined the molecular mechanisms of resistance to kanamycin and vi omycin in Mycobacterium smegmatis. All of the M. smegmatis strains wit h high:level kanamycin resistance had a nucleotide substitution from A to G at position 1389 of the 16S rRNA gene (rrs). This position is eq uivalent to position 1408 of Escherichia coli, and mutation at this po sition is known to cause aminoglycoside resistance. Mutations from G t o A or G to T at position 1473 of the M. smegmatis rrs gene were found in viomycin-resistant mutants which had been designated vicB mutants in our earlier studies, Using the M. smegmatis conjugation system, we confirmed that these mutations indeed contributed to kanamycin and vio mycin resistance, and kanamycin susceptibility was dominant over resis tance in a heterogenomic strain, Additional experiments showed that th ree of four Mycobacterium tuberculosis strains,vith high-level kanamyc in resistance had a mutation from A to G at position 1400, which was e quivalent to position 1389 of M. smegmatis.