[In vitro bactericidal rate of amikacin at concentrations realizable in vivo]

The bactericidal rate of amikacin in vitro was established by varying bacterial cell density (10(5) and 10(6) CFU/ml) and physiological state (lag phase and onset of exponential growth) at the moment the antibiotic was introduced. This was done with nine strains belonging to five different species. Antibiotic concentrations were those obtained in vivo at the valley (4 micrograms/ml) and the peak (20 micrograms/ml) with a dosage of 5 mg/kg. The concentration of 40 micrograms/ml is the peak value in the context of hypothesis of a short-term treatment with reinforced dosage (10 mg/kg). The bactericidal effect of amikacin, generally rapid, increased with increasing drug concentration. A bactericidal effect of 99.9% or even 99.99% was obtained in one hour or less at the concentration of 40 micrograms/ml. Above all, this concentration prevented regrowth or rebound, observed at lower concentrations. This results from a rapid but above all powerful bactericidal effect, practically total and constitutes a bacteriological argument in favor of an increase in dosage combined with a reduction in the length of treatment.