[In vitro antibacterial activity of 2 new quinolones: A 56619 (difloxacin) and A 56620. Comparison with pefloxacin, ofloxacin and ciprofloxacin]

Abstract

Minimal inhibitory concentration (MIC) of two new quinolones, A 56619 (difloxacin) and A 56620 were evaluated by agar dilution for 511 bacterial strains, in comparison with pefloxacin (PEF), ofloxacin (OFL) and ciprofloxacin (CIP). For Enterobacteriaceae, A 56620 (MIC 50 and 90 p. 100: 0,12 and 2 micrograms/ml) was less active than CIP (0,03 and 1) and more active than OFL (0,12 and 4) whereas A 56619 (1 and 16) appeared slightly inferior to PEF (0,25 and 8); the same range of activity was observed for Pseudomonas aeruginosa: CIP: 0,12-0,5; A 56620: 0,5-2; OFL and PEF: 1-4; A 56619: 1-8. For the majority of Acinetobacter (mode MIC: 0,5-1), Haemophilus (0,008-0,016), Meningococci (less than or equal to 0,008), Gonococci (0,06 à 0,25) and Legionella (0,12), activity of the two new compounds appeared very similar to those of the three other quinolones. A 56619 and A 56620 had a good activity (mode MIC: 0,25-0,5 micrograms/ml), similar to those of the three other quinolones, on Staphylococci sensitive strains whereas they were inactive on resistant strains. For Streptococci, A 56620 is about two times superior to A 56619; its activity is similar to that of PEF for Enterococci (mode MIC: 4) and to that of CIP on Streptococci A and Pneumococci (mode MIC: 0,5-1). For anaerobes, the two compounds had about the same activity similar to that of OFL and CIP (C. perfringens: 0,25-0,5 and B. fragilis: 4 micrograms/ml).