AMPLIFICATION AND NUCLEOTIDE-SEQUENCE OF THE QUINOLONE RESISTANCE-DETERMINING REGION IN THE GYRA GENE OF MYCOBACTERIA

Chromosomal DNA of different species of mycobacteria, Mycobacterium tu berculosis, Mycobacterirtm leprae, Mycobacterium avium and Mycobacteri um smegmatis, has been submitted to polymerase chain reaction using tw o oligonucleotide primers highly homologous to DNA sequences flanking the quinolone resistance-determining region in the gyrA gene of Escher ichia coli and Staphylococcus aureus. For each of these mycobacterial species, a 150-bp DNA fragment hybridizing with an intragenic probe of the gyrA gene of E. coli K12 was obtained. The nucleotide sequences o f the 108-bp fragments amplified from M. tuberculosis and M. avium wer e determined. The two sequences were 87% homologous. Except for one re sidue, their deduced amino acid sequences were identical and shared 67 % homology with the quinolone resistance-determining region of the gyr ase A subunits of E. coli and S. aureus. Sequencing of the 108-bp,frag ment amplified from an in vitro mutant of M. avium, highly resistant t o fluoroquinolones, showed a point mutation leading to the substitutio n of Ala for Val at a position corresponding to residues involved in q uinolone resistance in E. coli and S. aureus, i.e. Ser 83 for E. coli and Ser 84 for S. aureus.