In vitro evaluation of ceftazidime (GR 20263), amikacin and sisomicin, in a model simulating serum pharmacokinetics of therapeutic doses.

The activity of ceftazidime, amikacin and sisomicin was investigated in an in vitro model using varying concentrations of antibiotic which mimic the serum levels of patients after the intramuscular administration of a 500, 250 and 70 mg dose respectively. Using this test, during the time of the agar MIC value correlation, ceftazidime, amikacin and sisomicin proved to be active against strains sensitive to 16 micrograms/ml, 8 micrograms/ml and 4 micrograms/ml respectively. Using the above concentrations as the cut-off points in defining the sensitivity of the strains, ceftazidime revealed the same level of activity as amikacin (6 and 5 resistant strains respectively out of the 185 tested) and proved much more active than sisomicin (48 resistant strains).