In vitro combination susceptibility testing for detecting clinical isolates of Acinetobacter baumannii by five kinds of antibiotics with sulbactam / 临床检验杂志

ABSTRACT

Objective To investigate the in vitro antibacterial activity of single cefoperazone,ceftazidime,imipenem,tigecycline and colistin and their combination with sulbactam against clinical isolates of Acinetobacter baumannii (A.baumannii).Methods Twentythree meropenem-resistant A.baumannii strains and 21 meropenem-sensitive strains from the Study for Monitoring Antimicrobial Resistance Trends (SMART) during 2011 and 2012 were collected,and their combination susceptibility tests were performed by the checkerboard dilution method.The fractional inhibitory concentration (FIC) index was calculated to evaluate the combination effect of antibiotics.Results No antagonism effect was observed for all of combinations.The combination of sulbactam with cefoperazone or tigecycline mainly produced synergistic effect on A.baumannii,and the strains with FIC index ≤0.5 accounted for 56.8％ and 50.0％,respectively.The combination of sulbactam with imipenem or colistin showed synergistic or partially synergistic effect on A.baumannii,and the strains with FIC index ＜ 1 accounted for 61.4％ and 52.3％,respectively.However,the combination of sulbactan with ceftazidime didn't show any interation,and the strains with FIC index ≥4 accounted for 63.6％.Conclusion The combination of sulbactam with cefoperazone has the best synergistic effect on A.baumannii,especially on carbapenem-sensitive A.baumannii.The combination of sulbactam with imipenem or tigecycline may enhance the antibacterial activity on carbapenem-resistant A.baumannii.The combination of sulbactam with imipenem or tigecycline may be helpful for the treatment of carbapenem-resistant A.baumannii infection.