Objective To investigate the serum typing and in vitro antibacterial activity of cefepime,imipenem,
cefoperazone/subactam,against
Pseudomonas aerugino sa (PSA).Methods All isolates were identified by Vitek microbe automatic instrum ent and API identifying system.PSA were classified by typing serum according to reagent kit specification.Drug sensitive tests used K-B paper disk diffusion an d broth quantitative dilution method in accordnace with NCCLS standards.ESBLs wa s detected by double disk synergy test.AmpC was detected by three-dimensional test.Results The classified rates of 100 PSA isolates were 83%;B type was 50%; G and E type were 9%and 6%
respectively.The positive rates of ESBLs and AmpC we re 37%and 15%.The drug resistance rates of levofloxacin,amikacin, imipenem, ce fepime, ceftazidime,
cefoperazone/subactam were 51%, 48%, 38%, 33%, 20%and 18%respectively.The inhibition rates of cefepime,cefoperazone/subactam and imip enem against PSA were 59%,43%and 15%respectively. Conclusion The main serum t ypies of PSA were B,G and E type.The zymogenic rates of PSA are very serious. Ra tional selection of antimicrobial agents should be initiated in accordance with results of drug sensitive tests.