Susceptibility of bacterial isolates to gatifloxacin and ciprofloxacin from clinical trials 1997-1998

MICs of gatifloxacin and ciprofloxacin against 3482 pre-treatment, clinical trial isolates collected during 1997-1998 are reported. These data suggest ed that gatifloxacin was four- to eight-fold more active than ciprofloxacin against Gram-positive bacteria, with gatifloxacin MIC(90)s less than or eq ual to 0.33 mg/l against Staphylococcus aureus and Streptococcus pneumoniae , and less than or equal to 1.0 mg/l versus viridans streptococci and Enter ococcus faecalis. Both quinolones had similar MIC(90)s versus Enterobacteri aceae (generally less than or equal to 0.38 mg/l, except 0.7-0.8 mg/l for C itrobacter freundii) and Pseudomonas aeruginosa (similar to 8 mg/l). A tota l of 78% P. aeruginosa had gatifloxacin MICs less than or equal to2 mg/l. G atifloxacin was more active than ciprofloxacin against Acinetobacter specie s and non-P. aeruginosa pseudomonads. Both had exceptional activity versus Haemophilus spp, Moraxella catarrhalis and Neisseria in gonorrhoeae. In sum mary, compared to ciprofloxacin, gatifloxacin had improved activity against Gram-positive bacteria and comparable activity against Gram-negative bacte ria. (C) 2000 Elsevier Science B.V. and International Society of Chemothera py. All rights reserved.