Gatifloxacin hydrochloride is against S. aureus MS5935 topoisomerase IV, E. coli NIHJ JC-2 DNA gyrase and HeLa cell topoisomerase II with IC ₅₀ values of 13.8 μg/ml, 0.109 μg/ml, and 265 μg/ml, respectively.Gatifloxacin hydrochloride is against S. aureus MS5935 topoisomerase IV, E. coli NIHJ JC-2 DNA gyrase and HeLa cell topoisomerase II with MIC values of 0.05 μg/ml, 0.0063 μg/ml, and 122 μg/ml, respectively.Gatifloxacin hydrochloride exhibits antibacterial activities for wild-type strains (MS5935, MS5952, MR5867 and MR6009) the first-, second-, third-, and fourth-step mutants with MIC values of 0.05 to 0.10 μg/ml, 0.20 μg/ml, 1.56 to 3.13 μg/ml, 1.56 to 6.25 μg/ml, and 50 to 200 μg/ml, respectively. Gatifloxacin hydrochloride displays the most potent activity against the second- and third-step mutants (MS5952, MR5867 and MR6009) except for the second-step mutant of strain MS5935.Gatifloxacin hydrochloride has potent activity against norA transformant NY12 (MIC, 0.39 μg/ml).Gatifloxacin hydrochloride (20-100 μM; 72 hours) significantly decreases insulin content to 60% at Day 1, and continues to be reduced to 50.1% and 44.7% at Day 3 by 20 μM and 100 μM Gatifloxacin hydrochloride, respectively.

Gatifloxacin hydrochloride (subcutaneous injection; 100 mg/kg; 3 times a day; 30 days) significantly decreases the number of lesions in mouse footpad with Nocardia brasiliensis .