Hypermutable and fluoroquinolone-resistant clinical isolates of Staphylococcus aureus

Over 124 methicillin-susceptible Staphylococcus aureus 0/74 fluoroquinolone-susceptible versus 5150 fluoroquinolone-resistant isolates were hypermutable. Hypermutable isolates combined mutations in gyrA, parC, and/or parE genes. One strain had a large deletion of the mutator mutS and mutL genes. No relevant mutation in mutS and mutL genes was found in the other isolates.