Abstract: Aim The postantibiotics effects (PAEs)induced by cefoperazone (CPZ)alone were to be compared with those induced by a 1:1 combination of CPZ and sulbactam(SBT).Methods Ail the clinical isolates selected, including every six isolates of E.coli, S.aureus, Proteus and P.aeruginosa, were proved to be beta-lactamase-producing strains by the Nitrocefin Test.The PAEs were determined by means of measurement of transmittance using AVANT AGE Microbiology System.Results Longer PAEs induced by the combination of CPZ and SBT were observed in each concentration, even in lower CPZ concentrations (1/2 and 1 MIC), the PAEs were significant longer than by CPZ alone.Conclusion The results suggest that the efficacy of CPZ combined with SBT is stronger than that of CPZ alone against the infections caused by beta-lactamase-producing isolates.

Key words: cefoperazone, sulbactam, postantibiotic effect, beta-lactamase