In vitro and in vivo antibacterial activities of E-4868, a new fluoroquinolone with a 7-azetidin ring substituent.
E-4868, (-)-7-[3-(R)-amino-2-(S)-methyl-1-azetidinyl]-1-(2,4- difluorophenyl)-1,4-dihydro-6-fluoro-4-oxo-3-quinolinecarboxylic acid, is a new fluoroquinolone with an azetidine moiety at the 7 position. The in vitro activity of E-4868 has been compared with those of ciprofloxacin, ofloxacin, and fleroxacin, while the activity of ciprofloxacin was used as reference for in vivo studies. The MICs of E-4868 for 90% of the isolates tested (MIC90s) were 0.06 to 0.5 microgram/ml against gram-positive organisms, including Staphylococcus, Streptococcus, and Enterococcus spp. In general, the in vitro potency of E-4868 against gram-positive bacteria was higher than those of all of the other fluoroquinolones tested. MIC90s against members of the family Enterobacteriaceae between 0.03 and 1 microgram/ml were observed, with the exception of those against Serratia marcescens and Providencia spp., and a MIC90 of 2 micrograms/ml against Pseudomonas aeruginosa was obtained. E-4868 inhibited 90% of the Clostridium spp. and Bacteroides spp. at 2 micrograms/ml and was twofold more active than ciprofloxacin. An increase in the Mg2+ concentration from 1 to 10 mM increased the MIC between two and three times. Human urine caused a significant decrease in activity of E-4868, which was more pronounced at pH 5.5 than at pH 7.2. The presence of serum also decreased the activity of E-4868. Fifty percent effective dose (ED50) values against experimental Escherichia coli HM-42 infections in mice were 3.9 mg/kg of body weight with E-4868 and 3.5 mg/kg of body weight with ciprofloxacin. Corresponding ED50 values against P. aeruginosa HS-116 were 93.2 and 107.8 mg/kg, respectively, and those against Staphylococcus aureus HS-93 were 6.5 and 44.6 mg/kg, respectively. In experimental infections with Streptococcus pneumoniae 84551, the ED50 value of E-4868 was 154.4 mg/kg, while ciprofloxacin proved totally inactive at a dose of 400 mg/kg. When E-4868 was administered orally at a dose of 50 mg/kg in mice, the area under the concentration-time curve (0 to 4 h) value was 28.4 microgram . h/ml, while an area under the concentration-time curve value of 2.3 microgram . h/ml was observed for ciprofloxacin at the same dose. In these studies, levels of the two agents in blood 1 h postadministration were 7.6 and 1.2 microgram/ml, respectively.
Guinea
J
J
Department of Sanitary Microbiology and Parasitology, Faculty of Pharmacy, University of Barcelona, Spain.
Robert
M
M
Gargallo-Viola
D
D
Xicota
M A
MA
Garcia
J
J
Tudela
E
E
Esteve
M
M
Coll
R
R
Pares
M
M
Roser
R
R
D000818:Animals; D000890:Anti-Infective Agents / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use; D001419:Bacteria / Q000187:drug effects*; D002939:Ciprofloxacin / Q000494:pharmacology / Q000627:therapeutic use; D003470:Culture Media; D016576:Fleroxacin / Q000494:pharmacology / Q000627:therapeutic use; D024841:Fluoroquinolones; D006736:Horses; D008297:Male; D051379:Mice; D008826:Microbial Sensitivity Tests; D015242:Ofloxacin / Q000494:pharmacology / Q000627:therapeutic use; D015363:Quinolones / Q000494:pharmacology* / Q000627:therapeutic use
D000890:Anti-Infective Agents; D003470:Culture Media; D024841:Fluoroquinolones; D015363:Quinolones; C081131:E-4868; D002939:Ciprofloxacin; D015242:Ofloxacin; D016576:Fleroxacin