DNA cloning and organization of the Staphylococcus aureus gyrA and gyrB genes: close homology among gyrase proteins and implications for 4-quinolone action and resistance.

Staphylococcus aureus gyrA and gyrB genes, which encode the DNA gyrase A and B proteins, have been isolated and found to map contiguously. DNA sequence analysis revealed close homology between the S. aureus gyrase subunits and their counterparts in Bacillus subtilis and Escherichia coli, including several conserved amino acid residues whose substitution in E. coli confers resistance to 4-quinolones. These results are discussed in regard to quinolone resistance mechanisms in S. aureus.