In vitro activity and mode of action of fluoroquinolones

The in vitro activity of nine fluoroquinolones has been determined by agar dilution method against 1100 clinical isolates of different microorganisms: 412 Enterobacteriaceae, 93 non-fermenters, 398 enteropathogens, 140 Gram-positive cocci, 31 Haemophilus and 26 gonococci. The bactericidal activity tested in broth against different representative isolates was generally similar to the inhibitory concentration. Killing kinetics studied in different isolates of Enterobacteriaceae, in Pseudomonas aeruginosa, Vibrio cholerae, Staphylococcus aureus and Streptococcus faecalis showed a very rapid bactericidal effect, after 2 to 8 h of contact, in all species except in Streptococcus faecalis.