Activity of gatifloxacin and ciprofloxacin in combination with other antimicrobial agents

Abstract The influence of non-quinolone antimicrobial agents on the antibacterial activities of gatifloxacin and ciprofloxacin was determined using chequerboard, fractional inhibitory concentration, (FIC) and time-kill analysis methods. In the chequerboard method, the quinolones were tested in combination with ten antimicrobial agents (macrolides, aminoglycosides, β-lactams, vancomycin, rifampicin and chloramphenicol) against five bacterial strains (one strain each of Staphylococcus aureus , Escherichia coli , Pseudomonas aeruginosa , Enterococcus faecalis and Streptococcus pneumoniae ). In no incidence was antagonism (FIC≥4) or synergy (FIC≤0.5) observed; all dual drug combinations involving gatifloxacin or ciprofloxacin showed additivity/indifference (FIC>0.5, E. faecalis These findings indicate that, with the exception of E. faecalis , the antibacterial activities of quinolones are generally additive/indifferent to those of other antimicrobial agents.