Contributions of the combined effects of topoisomerase mutations toward fluoroquinolone resistance in Escherichia coli

Antimicrob Agents Chemother. 2007 Nov;51(11):4205-8. doi: 10.1128/AAC.00647-07. Epub 2007 Aug 6.


In defined, isogenic strains, at least three mutations, two of which must be in gyrA, were required to exceed the CLSI breakpoint for fluoroquinolone resistance. Strains with double mutations in both gyrA and parC had even higher MICs of fluoroquinolones than strains with totals of three mutations.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA Topoisomerases / genetics*
  • Drug Resistance, Bacterial / genetics*
  • Escherichia coli / drug effects*
  • Escherichia coli / genetics*
  • Fluoroquinolones / pharmacology*
  • Microbial Sensitivity Tests
  • Mutation*


  • Fluoroquinolones
  • DNA Topoisomerases