In vitro antimicrobial activity of cefazolin combined with sulbactam against 90 clinical isolates pr

Antimicrobial activity of cefazolin (CEZ) combined with a beta-lactamase inhibitor sulbactam (SBT) against beta-lactamase producing strains of clinical isolates was studied in vitro using liquid dilution method compared with cefazolin alone. 90 isolates mainly with Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae were identified to produce betalactamase by the chromogenic cephalosporin nitrocefin. Among 90 betalactamase producing strains of clinical isolates 37.8% were resistant to cefazolin alone (MIC≥32mg/L), while only 21.1% isolates were resistant to cefazolin+sulbactam (CEZ/SBT) (2∶1), P<0.05. The combination of cefazolin with sulbactam (2∶1) showed significant synergistic effect against 65.6% of the strains, lowered MIC 2-128 folds compared with that of cefazolin alone, including 73.5% of strains which were resistant to cefazolin. In addition, the ratio of CEZ/SBT of 2∶1 resulted in much better antimicrobial effect than that of 1∶1 (the results of 35 strains).