Activity of E-3846, a new fluoroquinolone, in vitro and in experimental cystitis and pyelonephritis in rats

The in vitro antibacterial activity of E-3846, a new fluoroquinolone carboxylic acid derivative with a pyrrol ring substituent at position 7, was evaluated in comparison with norfloxacin and ciprofloxacin. E-3846 was more active than the reference quinolones against Staphylococcus species, including methicillin-resistant strains. E-3846 was similar to ciprofloxacin and more active than norfloxacin against Streptococcus (Enterococcus) faecalis. In general, E-3846 was more active than norfloxacin against members of the family Enterobacteriaceae, but less active than ciprofloxacin. For Pseudomonas aeruginosa, the MICs giving 90% inhibition for E-3846, norfloxacin, and ciprofloxacin were 2, 1, and 0.25 micrograms/ml, respectively. The activity of E-3846 increased at acid pH; in contrast, acid pH caused a pronounced decrease in the activity of norfloxacin and ciprofloxacin. In vivo, E-3846 demonstrated excellent therapeutic efficacy in treating experimental S. faecalis, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Pseudomonas aeruginosa cystitis and pyelonephritis in rats.