Bactericidal activity of ceftazidime against Pseudomonas aeruginosa under conditions simulating serum pharmacokinetic

The bactericidal activity of ceftazidime against Pseudomonas aeruginosa was evaluated in an in-vitro model simulating serum pharmacokinetics. Strains were exposed to initial concentrations of 110 mg/l (as achieved in serum after 1 g i.v. ceftazidime) and the antibiotic was removed constantly at T(1/2) of 1.9 h. Rapid bactericidal activity was observed but stopped before the concentration dropped below the minimum bactericidal level. The time required by the strains to recover from the lethal ceftazidime effect ranged from 2.6 to > 5 h. When the strains were exposed to concentrations of 32 initial mg/l and T(1/2) of 60 min the bactericidal activity continued even after the level dropped below the minimum inhibitory concentration.