title: Differential selection of multidrug efflux mutants by trovafloxacin and ciprofloxacin in an experimental model of Pseudomonas aeruginosa acute pneumonia in rats.
abstract: The ability of trovafloxacin and ciprofloxacin to select efflux mutants in vivo was studied in a model of acute Pseudomonas aeruginosa pneumonia in rats. Twelve hours after intratracheal inoculation of 10(6) CFU of P. aeruginosa strain PAO1 enmeshed in agar beads, two groups of 12 rats were treated by three intraperitoneal injections of each antibiotic given every 5 h. Dosing regimens were chosen to obtain a comparable area under the concentration-time curve from 0 to infinity/MIC ratio of 27.9 min for trovafloxacin (75 mg/kg of body weight) and of 32.6 min for ciprofloxacin (12.5 mg/kg). Twelve rats were left untreated and served as controls. Rats were sacrificed 12 h after the last injection (34 h after infection) for lung bacteriological studies. Selection of resistant bacteria was determined by plating lung homogenates on Trypticase soy agar plates containing antibiotic. In untreated animals, the frequency of resistant colonies was 10-fold higher than in agar beads. Compared to controls, both treatment regimens resulted in a 2-log reduction of lung bacterial load. The frequency of resistant colonies was 10-fold less with trovafloxacin than with ciprofloxacin at twice the MIC (7.4 x 10(-5) versus 8.4 x 10(-4), respectively) (P < 0.05) and at four times the MIC (6.2 x 10(-4) versus 5.0 x 10(-5), respectively) (P < 0.05). A multidrug resistance phenotype typical of efflux mutants was observed in all 41 randomly tested colonies obtained from treated and untreated rats. In agreement with in vitro results, trovafloxacin and ciprofloxacin preferentially selected MexCD-OprJ and MexEF-OprN overproducers, respectively. These results demonstrate the differential ability of trovafloxacin and ciprofloxacin to select efflux mutants in vivo and highlight the rapid emergence of those mutants, even without treatment.
authors.affiliation: INSERM EPI 9933, Hôpital Bichat-Claude Bernard, 75018 Paris, France. ojlamber@club-internet.fr
authors.forename: O F
authors.initials: OF
authors.lastname: Join-Lambert
authors.forename: M
authors.initials: M
authors.lastname: Michéa-Hamzehpour
authors.forename: T
authors.initials: T
authors.lastname: Köhler
authors.forename: F
authors.initials: F
authors.lastname: Chau
authors.forename: F
authors.initials: F
authors.lastname: Faurisson
authors.forename: S
authors.initials: S
authors.lastname: Dautrey
authors.forename: C
authors.initials: C
authors.lastname: Vissuzaine
authors.forename: C
authors.initials: C
authors.lastname: Carbon
authors.forename: J
authors.initials: J
authors.lastname: Pechère
mesh_terms: D000208:Acute Disease; D000818:Animals; D000890:Anti-Infective Agents / Q000493:pharmacokinetics / Q000627:therapeutic use*; D002939:Ciprofloxacin / Q000493:pharmacokinetics / Q000627:therapeutic use*; D004352:Drug Resistance, Microbial; D018432:Drug Resistance, Multiple / Q000235:genetics*; D024841:Fluoroquinolones; D008168:Lung / Q000382:microbiology / Q000473:pathology; D008297:Male; D009154:Mutation / Q000235:genetics; D009287:Naphthyridines / Q000493:pharmacokinetics / Q000627:therapeutic use*; D018410:Pneumonia, Bacterial / Q000188:drug therapy* / Q000382:microbiology / Q000473:pathology; D011550:Pseudomonas aeruginosa; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000890:Anti-Infective Agents; D024841:Fluoroquinolones; D009287:Naphthyridines; D002939:Ciprofloxacin; C080163:trovafloxacin