Using LKB-2277 bioactivity monitor, the inhyibitory action of three fluoroquinolones on Escherichia coli growth was investigated at 37℃. The three fluoroquinolones were Lomefloxacin, Norfloxacin and Pefloxacin. In accordance with thermokinetic model, the relationships of the drugs, such as k～c, P~m~a~x～k and I%～c, were obtained. half inhibitory concentrations of the drugs, Ic~5~0, were obtained by quantitative analysis. from the view of thermodynamics, the relationship between quantity and effect of fluoroquinolones was investigated, which showed paradioxical effect (PE) situation. Th action mechanism of apradioxical effect was also studied.

Key words: ESCHERICHIA COLI, THERMOCHEMISTRY, QUANTITATIVE STRUCTURE ACTIVITY RELATIONSHIP