Greater ciprofloxacin tolerance as a possible selectable phenotype underlying the pandemic spread of the H30 subclone of Escherichia coli sequence type 131

Antimicrob Agents Chemother. 2015 Nov;59(11):7132-5. doi: 10.1128/AAC.01687-15. Epub 2015 Aug 31.


Minimum bactericidal concentrations (MBCs) for ciprofloxacin were significantly higher among 41 members of the H30 subclone within Escherichia coli sequence type 131 than among 48 other fluoroquinolone-resistant E. coli isolates. This MBC difference, which was not explained by ciprofloxacin MICs, gyrA, parC, and parE mutations, the presence of aac(6')-Ib-cr, or organic solvent tolerance (a surrogate for efflux pump activity), conceivably could have promoted the pandemic emergence of the H30 sequence type 131 subclone.

Publication types

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

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Ciprofloxacin / pharmacology*
  • DNA Gyrase / genetics
  • Escherichia coli / drug effects*
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Escherichia coli Infections / microbiology
  • Escherichia coli Proteins / genetics
  • Fluoroquinolones
  • Microbial Sensitivity Tests
  • Mutation


  • Anti-Bacterial Agents
  • Escherichia coli Proteins
  • Fluoroquinolones
  • Ciprofloxacin
  • DNA Gyrase