ObjectiveTo detect the distribution of resistancenodulation (RND) efflux pump system of Acinetobacter baumannii(AB), and explore the relationship between its’ expression and antimicrobial resistance.MethodsFiftynine strains of multidrugresistant AB isolated from clinical specimens in The First Affiliated Hospital of Nanchang University were identified and performed antimicrobial susceptibility analysis, distribution of RND efflux system of AB was detected by polymerase chain reaction(PCR), expression of efflux pump genes in different drugresistant phenotypes of AB was compared, relationship between the expression level and drug resistance was analyzed, amplified products of RND efflux system were sequenced.ResultsResistance rates of AB to ampicillin/sulbactam, imipenem, gentamicin, ciprofloxacin, and levofloxacin were 93.2%, 94.9%, 88.1%, 96.6%, and 52.5% respectively. PCR detection results of efflux pump and integron genes of 59 AB strains revealed that the carrying rates of adeR, adeS, adeB, adeJ, and adeG genes were 81.4%, 91.5%, 93.2%, 100.0%, and 61.0% respectively. The expression of efflux pump genes in different strains was different, expression levels of adeB and adeJ genes among gentamicin, imipenem, ampicillin/sulbactam resistant AB group and nonresistant AB group were significantly different (all P<0.05). There was no mutation or insertion sequence in the base sequences of regulatory genes adeR and adeS of adeABC efflux pump.ConclusionRND efflux pump system is universally present in AB, the expression upregulation of adeB and adeJ genes in RND efflux pump system is related with antimicrobial resistance of bacteria to gentamycin, imipenem, and ampicillinsulbactam.