Comparison of in vitro antibacterial activities for different ratio of amoxicillin/sulbactam

Objective:To evaluate the antibacterial activities in vitro of amoxicillin/sulbactam (2:1 and 4:1). Methods:Minimal inhibitory concentrations (MIC) were determined by agar double dilution. Of 620 strains of clinical organisms, 502 cultures of organisms were found to be able to produce β-lactamases (80.97%). Results:Two combinations of amoxicillin/sulbactam (2:1 and 4:1) all showed resistant antibacterial activities with fluctuated MIC range,MIC50 and MIC90 in 1-2 times on the following organisms: Escherichia coli of ESBL, Klebsiella pneumoniae of ESBL, Enterobacter spp producing AmpC enzyme and non-fermentation gram negative rod ( Pseudomonas aeruginosa , Acineto-bacter spp, Stenophotomonas maltophilus). Two combinations of amoxicillin/sulbactam (2:1 and 4:1) also gave an equivalent titer in the MIC range,MIC50 and MIC90 on common pathogenic bacteria that cause community infection,i.e. ,Haemophilus Influenza producing β-lactamases,Moraxella catarrh , MSSA and MSSCoN, Streptococcus pneumoniae, β-haemolysis Streptococcus and Enterococcus fae-calis. Conclusion: Amoxicillin/sulbactam (4:1) was found to have the same antibacterial activity as amoxicillin/sulbactam (2:1).