Abstract:

Objective To analyze the sensitivity of Acinetobacter baumannii （A. baumannii） to common antibiotics， and to detect the expression level of efflux pump genes and outer membrane protein （OMP） genes and to explore the relationship between the expression of these genes and antibiotic resistance. Methods A total of 213 isolates of multidrug?resistant A. baumannii from the lower respiratory tract of inpatients from our hospital were collected. Susceptibility testing was conducted by K?B disk diffusion method. According to the drug sensitivity test， they were divided into non?sensitive groups （NS groups） and sensitive groups （S groups）. The expression level of efflux pump genes （adeB， adeJ， adeG， craA， abeM， amvA） and OMP genes （omp25， omp33?36， carO） were detected by fluorescence quantitative PCR， and the differences of these genes between NS groups and S groups were compared. Results The insensitive rates of A. baumannii to amikacin and imipenem were 89.2% and 81.2% respectively， and the insensitive rates to piperacillin/tazobactam， cefoperazone/ sulbactam and gentamicin were more than 92%. The distribution of increased relative expression of adeB gene （RE≥1） in NS and S groups of antibiotics （AMK， IPM， CFP， FEP， TZP， CAZ， SXT， CIP， SCF， CN） was analyzed respectively. The results showed that the proportion of RE ≥ 1 in most antibiotic NS groups was significantly higher than that in S groups， suggesting that the overexpression of adeB was closely related to the above?mentioned antibiotic resistance. The RE values of adeB gene mRNA of efflux pump were significantly different in the following antibiotics （AMK， IPM， CFP， FEP， TZP， CAZ， CIP， SCF， CN） between NS groups and S groups respectively. The RE values of efflux pump genes （adeJ， adeG， craA， abeM and amvA） in the two groups had no elevation， and there was no statistical difference between the two groups by comparative analysis. The average RE values of OMP genes （omp25， omp33?36， carO） were all more than 1.0， indicating an increasing of relative expression. Conclusion The A. baumannii is highly resistant to many kinds of antibiotics. The overexpression of efflux pump gene adeB plays an important role in drug resistance of A. baumannii in our hospital， while other efflux pump genes （adeJ、adeG、craA、abeM、amvA） and OMP genes （omp25， omp33?36， carO） may not effect in most isolates of the drug resistance mechanism in this study.

Key words: Acinetobacter baumannii, drug resistance, efflux pump, outer membrane protein