[Effect of superinhibitory levels of imipenem and amikacin singly or in combination on Pseudomonas aeruginosa].

Suppression of bacterial growth of a clinical Pseudomonas aeruginosa strain after 30 min treatment with imipenem and amikacin alone as well as after treatment with a combination of these antibiotics (postantibiotic effect-PAE) was studied. Imipenem (2xMIC) induced PAE lasting 0.7 h, at a concentration of 4xMIC caused suppression of bacterial growth for 1.5 h. The effect of suprainhibitory concentrations of amikacin was more substantial. Amikacin (2x or 4xMIC) manifested PAE of 1.9 h or 4.0 h. The postantibiotic effect induced by antibiotic combination-imipenem (2xMIC) + amikacin (2xMIC) (3.0 h) as well as imipenem (4xMIC) + amikacin (2xMIC) (4.0 h) was longer than the mathematical sum of the postantibiotic effects produced by individual antibiotics at the mentioned concentrations (2.6 h or 3.4 h). Prolongation of the suppression of bacterial growth induced by a combination of imipenem (2xMIC) + amikacin (2xMIC) was 15.4%, and 17.6% after treatment with a combination of imipenem (4xMIC) + amikacin (2xMIC).