The pharmacodynamic effect of amoxicillin and danofloxacin against Salmonella typhimurium in an in-vitro pharmacodynamic model

The pharmacodynamic effect of amoxicillin and danofloxacin against two stra ins of Salmonella typhimurium was examined in an in-vitro pharmacodynamic m odel. For amoxicillin, peak concentrations of 1, 2 and 4 mu g ml(-1) and half-liv es (t(1/2) of 3 and 15 hours were evaluated. For danofloxacin peak concentr ations of 0.25, 0.50 and 1.50 mu g ml(-1) and half-lives of 7 and 15 hours were examined. For amoxicillin both the peak concentration and the half-lif e influenced the pharmacodynamic effect (P < 0.001). Maximal pharmacodynami c effect was observed when the antibiotic concentration was greater than mi nimum inhibitory concentration for 79 per cent or more of the dosing interv al. The hires of the isolates increased when the amoxicillin concentrations were close to the nac during the first hours of exposure. For danofloxacin the pharmacodynamic effect was dependent on the peak conce ntration only (P < 0.001). Increases in MIC were found in two cases with th e less susceptible strain, where peak concentration/MIC ratios were equal t o or less than 4.