Distribution of Carbapenemases and Efflux Pump in Carbapenem-resistance Acinetobacter baumannii.

Acinetobacter baumannii has emerged as an important pathogen related to serious infections and nosocomial outbreaks around the world. In this study, 100 isolates of carbapenem-resistance in Acinetobacter baumannii (CRAB) were collected from clinical specimens. Agar dilution was conducted to determine the minimum inhibitory concentrations (MICs) for 15 kinds of antibiotics. Genes of carbapenemases and efflux pumps were amplified by PCR. The expression difference of pump genes was analyzed by real-time PCR between CRAB and carbapenems-sensitive Acinetobacter baumannii (CSAB). We found that most antibiotics, including aminoglycosides, fluoroquinolones, and cephalosporins showed high MIC values in CRAB. All isolates were sensitive to polymyxin B. Among the CRAB specimens, 54, 32 and 16 isolates were positive for SHV-12, PER-1 and TEM-1, respectively. 86 isolates were positive for OXA-23. 55 and 33 isolates carried adeB and adeJ genes, respectively. The expression level of adeB in CRAB was ten times higher than that in CSAB. We speculate that SHV-12, PER-1, TEM-1, OXA-23 and the AdeABC efflux pump may participate in high-level carbapenems resistance in Acinetobacter baumannii Moreover, adeE may be related to low-level resistance of carbapenems and quinolones in Acinetobacter baumannii.