Abstract: AIM: To compare in vitro activity of gatifloxacin against 182 clinical isolated pathogens with those of ciprofloxacin, ofloxacin, levofloxacin and sparfloxacin.METHODS: The MICs of 182 clinical isolated pathogens were determined by the two-fold agar dilution method.RESULTS: The MIC90 of gatifloxacin against staphylococcus species was lower than the other four fluoquinolones. The ratio of sensitivity of staphylococcus species to gatifloxacin was higher than the other four fluoquinolones;the MICR of gatifloxacin against other gram-positive cocci was lower than the other four fluoquinolones.The ratios of sensitivity of gram-negative bacilli, such as Escherichia species and Enterobacter species to gatifloxacin were higher than the other four fluoquinolones;The MIC90 of gatifloxacin against escherichia species and enterobacter species was 2 fold lower than levofloxacin and 8 fold lower than the other 3 fluoquinolones.The ratios of sensitivity of pseudomonas species, klebsiella species and other gramnegative bacilli to gatifloxacin had no significance with levofloxacin and were higher than ciprofloxacin, ofloxacin, and sparfloxacin.CONCLUSION: In vitro activity of gatifloxacin against common clinical bacterium is strong.

Key words: gatif loxacin, in vitro activity, fluoquinolones, clinical isolates