title: Mutant selection window in levofloxacin and moxifloxacin treatments of experimental pneumococcal pneumonia in a rabbit model of human therapy.
abstract: For some pneumococci the fluoroquinolone MICs are low but the mutant prevention concentrations (MPCs) are high; this difference defines in vitro the mutant selection window (MSW). We investigated in vivo the bacterial reduction and the occurrence of resistant mutants with moxifloxacin (MFX; 400 mg once daily) or levofloxacin (LVX; 500 mg twice daily) in treatments similar to those in humans with experimental pneumonia due to pneumococci (expPP) exhibiting various MICs and MPCs. The MIC/MPC for MFX and LVX and genotypes were as follows: strain 16089, 0.125/0.125 and 0.5/0.5 (wild type); strain MS1A, 0.25/0.25 and 1/2 (efflux); strain MS2A, 0.25/4 and 1.75/28 (parC79); strain MR3B4, 0.25/4 and 2/32 (parC79); strain M16, 0.5/2 and 8/32 (parC83); strain Gyr-1207, 1.5/3 and 8/16 (gyrA); and strain MQ3A, 4/4 and 16/64 (parC and gyrA). Both drugs were efficient with wild type-expPP, but only MFX was efficient with efflux-expPP. No bacterial reduction was observed for parC-expPPs due to mutants observed in 18 to 100% of animals, depending on the strain and the drug tested. These mutants showed unbound area under the concentration-time curve and MICs of from 50 to 164 for MFX. The in vivo pharmacodynamic boundaries of the MSW were different for MFX and LVX. We conclude that, after LVX or MFX treatment, mutants occur in vivo if there is a preexisting parC mutation, since the drug concentrations fall below the MPCs of these strains. Since the MPC determination cannot be routinely determined, these phenotypes or genotypes should be detected by simple tests to guide the therapeutic options.
authors.affiliation: Service des Maladies Infectieuses, Microbiologie Médicale et Moléculaire, Hôpital du Bocage, 21034 Dijon Cedex, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Croisier
authors.forename: Manuel
authors.initials: M
authors.lastname: Etienne
authors.forename: Emilie
authors.initials: E
authors.lastname: Bergoin
authors.forename: Pierre-Emmanuel
authors.initials: PE
authors.lastname: Charles
authors.forename: Catherine
authors.initials: C
authors.lastname: Lequeu
authors.forename: Lionel
authors.initials: L
authors.lastname: Piroth
authors.forename: Henri
authors.initials: H
authors.lastname: Portier
authors.forename: Pascal
authors.initials: P
authors.lastname: Chavanet
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000493:pharmacokinetics / Q000627:therapeutic use*; D019540:Area Under Curve; D001372:Aza Compounds / Q000493:pharmacokinetics / Q000627:therapeutic use*; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D024841:Fluoroquinolones; D006801:Humans; D064704:Levofloxacin; D008168:Lung / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D000077266:Moxifloxacin; D009154:Mutation; D015242:Ofloxacin / Q000493:pharmacokinetics / Q000627:therapeutic use*; D011018:Pneumonia, Pneumococcal / Q000188:drug therapy* / Q000382:microbiology; D011804:Quinolines / Q000493:pharmacokinetics / Q000627:therapeutic use*; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000187:drug effects / Q000235:genetics
chemical_list: D000890:Anti-Infective Agents; D001372:Aza Compounds; D004269:DNA, Bacterial; D024841:Fluoroquinolones; D011804:Quinolines; D064704:Levofloxacin; D015242:Ofloxacin; D000077266:Moxifloxacin