Abstract: Objective　To study the relationship between resistance and active efflux pump in imipenemresistant Acinetobacter baumannii (IRAB)， and guide the rational use of antibiotics and the control of nosocomial infections. Methods　A total of 50 IRAB and 30 imipenemsensitive Acinetobacter baumannii(ISAB) were collected from clinical specimens. The minimum inhibitory concentrations (MIC) to 13 antibiotics were determined by agar dilution method, and the changes of MIC in imipenem by adding PheArgbetaNaphthylamide（PAβN， a kind of pump inhibitor） were observed. Homology was analyzed by pulsefield gel electrophoresis (PFGE）. The adeB， adeR， adeS， adeJ and abeM genes were amplified by polymerase chain reaction (PCR). Results　In 50 IRAB， the antibiotics of MIC50>128 μg/mL included amikacin， ciprofloxacin， piperacillintazobactam， cefoperazone， cefoxitin， tetracycline and sulfamethoxazole. The antibiotics of MIC50 from 32 to 128 μg/mL included meropenem， cefoperazonesulbactam， cefepime， ceftazidime， ceftriaxone and cefotaxime. The antibiotics of MIC50<8 μg/mL included levofloxacin and polymyxin B. In 30 ISAB， the antibiotics of MIC50<8 μg/mL included meropenem， amikacin， ceftazidime， cefepime， cefoperazonesulbactam and polymyxin B. The MIC of 33(66%) IRAB in imipenem decreased 4 to 32 times after adding PAβN， while ISAB had no obvious changes. According to PFGE，80 isolates could be classified into 7 types， and type A was the major clone. By PCR amplification， the detection rates of adeB， adeR， adeS， adeJ and abeM genes were >80% in IRAB. There were significant differences in all genes compared with those of ISAB(P<0.01). Conclusions　There is an endemic of IRAB in Renji Hospital, and AdeABC， AdeIJK and AbeM efflux pump widely exist.

Key words: Imipenemresistant Acinetobacter baumannii, Active efflux pump, Resistance mechanism