TOPOISOMERASE MUTATIONS IN FLUOROQUINOLONE-RESISTANT AND METHICILLIN-SUSCEPTIBLE AND METHICILLIN-RESISTANT CLINICAL ISOLATES OF STAPHYLOCOCCUS-AUREUS

The incidence of the various mutations in the genes encoding topoisome rase IV and DNA gyrase in fluoroquinolone-resistant clinical isolates of Staphylococcus aureus is not known. Using restriction fragment leng th polymorphism analysis and DNA sequencing, we found that in fluoroqu inolone- and methicillin-resistant strains, mutations in grlA and gyrA are quite likely to be present together. For fluoroquinolone-resistan t but methicillin-susceptible strains, mutations in grlA alone are mor e common.