In Vitro Activity of Gatifloxacin

OBJECTIVE:The in vitro activity of gatifloxacin against 1222 clinical isolated pathogens was evaluated and compared with those of ciprofloxacin, ofloxacin and sparfloxacin. METHODS: MICs were determined by the twofold agar dilution method. MBCs were determined, by the twofold broth dilution method. (NCCLS, 1999) RESULTS: The results showed that gatifloxacin inhibited 90%(MIC90) of gram-negative bacilli tested at O.5mg.L-1 was compared to ciprofloxacin. The MIC90 of gatifloxacin against Klebsiella pneumonia, Enterbacter cloacae, Proteus spp., Shigella spp., were 0.062, 0.062, 0.5 and O.25mg.L-1 respectively, but 90% of E.coli were inhibited at 8mg.L-1, ratio of resistance was 58%. ciprofloxacin-resistant E.coli were also resistant to gatifloxacin. gatifloxacin inhibited 90% of Acinetobacter calcoaceticus, Pseudomoneas aeruginosa and Xanthomonas maltopholia at 0.062, 2 and 1mg·L-1 respectively, was equal to ciprofloxacin. gatifloxacin showed greater activity against gram-positive bacteria than ciprofloxacin and ofloxacin. The MIC90 of gatifloxacin against MSSA, Streptococcus pyogenes and Streptococcus pneumonia were 0.125, 0.125 and 0.5mg.L1, respectively. Its activities were similar to sparfloxacin. 90% of MRSA tested were inhibited at 4mg.L-1 90% of Staphylococcus epidermidis at 0. 5mg.L-1 Haemophilus influenzae was very susceptible to gatifloxacin. The value of MIC90 was O.Ol6mg.L-1. gatifloxacin inhibited 90% of Bacteroid frgilis at 1mg.L-1 its activity was equal to sparfloxacin and higher than ciprofloxacin and ofloxaxin. CONCLUSION: gatifloxaxin was as active as ciprofloxacin against gram-negative bacilli. Against grain-positive cocci gatifloxacin was more active than ciprofloxacin and ofloxacin. There was no significant effect of inoculum size and human serum on MIC. The activities of gatifloxacin against E.coli, Klebsiells pneumomia, Pseudomonas aeruginosa and Staphylococcus aureus were decreased by acidic pH. Gatifloxacin had excellent bactericidal activity.