Frequency of 1st- and 2nd-step topoisomerase mutations in Streptococcus pneumoniae following levofloxacin and moxifloxacin exposure

Laurie B. Hovde, Dana A. Simonson, John C Rotschafer

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

Seven Streptococcus pneumoniae isolates were exposed to inhibitory concentrations of levofloxacin and moxifloxacin in antibiotic-containing agar dilution plates. Colony counts were used to calculate the frequency of mutation. DNA was sequenced to detect mutations in the quinolone resistance-determining regions of the gyrA, gyrB, parC, and parE genes. The wild-type S. pneumoniae isolate developed a parC mutation after exposure to levofloxacin more frequently than it developed a gyrA mutation after exposure to moxifloxacin. The 1st-step gyrA mutant developed a 2nd-step gyrA-parC mutation more frequently after exposure to levofloxacin. Conversely, the transformation from a 1st-step parC mutant to a 2nd-step parC-gyrA mutant occurred more frequently following exposure to moxifloxacin. Our data suggest that the occurrence of a 2nd mutation will be contingent on the location of the 1st mutation and the preferential binding site of the fluoroquinolone that drives the transformation from 1st- to 2nd-step mutant.

Original languageEnglish (US)
Pages (from-to)295-299
Number of pages5
JournalDiagnostic Microbiology and Infectious Disease
Volume60
Issue number3
DOIs
StatePublished - Mar 1 2008

Keywords

  • DNA gyrase
  • Levofloxacin
  • Moxifloxacin
  • Streptococcus pneumoniae
  • Topoisomerase IV

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