[Theoretical bases for the combination of ceftazidime with other antibiotics. Synergism research].

Combinations of antibiotics have always been difficult to study, and the available methods often give discordant results making interpretation uneasy in the absence of in vitro-in vivo correlations. By studying the bactericidal effects of combinations a better definition of interactions between two antibiotics can be obtained if the concept of dominance is taken into account. Ceftazidime, a time-dependent antibiotic, acts synergistically with aminoglycosides, notably against moderately sensitive strains. This synergistic effect results from acceleration of the early bacterial kill and from blockage of the late regrowths. With quinolones, the synergistic effect does not result from blockage of late regrowths. However, the significance of these results needs to be confirmed by clinical trials.