Objective:To investigate the changes in the pattern of antimicrobial resistance among gram-negative bacilli isolated from our hospital in the past 3 years in an effort the select the optimal antimicrobial therapy.Methods:The susceptibility to antimicrobial therapy was tested by CLSI-recommended disk diffusion method in 8237 stranis of gram-negative bacilli isolated from inpatients from 2005 to 2007.The data were analyzed by WHONET 5.3 software.Results:The most common gram-negative was Pseudomonas aeruginosa(45.4%) followed by Acinetobacter baumannii(15.5%)

Escherichia coli(13.2%)

Klebsiella pneumoniae(11.8%) and Stenotrophomonas maltophilia(7.7%).The antimicrobial agents with a higher sensityvity to gram-negative bacilli were carbapenems

amikacin

piperacillin-tazobactam and ceftazidime.The prevalence of extended spectrum-lactamases(ESBLs) was significantly higher in Escherichia coli and in Klebsiella pneumoniae.Conclusion:The resistant rate of gram-negative bacilli isolated during 3 years is increasing rapidly.It is very important to enhance the drug resistance monitoring and select the optimal antibiotics therapy.