Laboratory Medicine ›› 2015, Vol. 30 ›› Issue (1): 53-57.DOI: 10.3969/j.issn.1673-8640.2015.01.013

Previous Articles     Next Articles

Epidemiology and resistance mechanism study of carbapenem-resistant Acinetobacter baumannii

ZHANG Guanghui1, CAO Xueping2, YU Jing2, LIU Ying2, GE Yan1   

  1. 1. Tongji University School of Medicine, Shanghai 200092, China
    2. Department of Clinical Laboratory, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China
  • Received:2014-10-09 Online:2015-01-30 Published:2015-02-02

Abstract:

Objective To understand the drug resistance mechanisms and epidemiology of carbapenem-resistant Acinetobacter baumannii in order to guide the rational use of antibiotics and to provide the reference for the control of nosocomial infections. Methods A total of 116 Acinetobacter baumannii (110 carbapenem-resistant isolates and 6 carbapenem-sensitive isolates) isolated from clinical specimens were classified and analyzed according to endemic areas and specimen types. The isolates were analyzed by repetitive-sequence polymerase chain reaction (REP-PCR) for genotyping. Beta-lactamase genes (OXA, IMP, VIM and soon) and efflux pump-encoding genes (adeA, adeB, adeC, adeJ, adeG) were amplified by PCR. Real-time fluorescence quantitation PCR was performed to compare the expression level of the efflux pump-encoding genes in resistant and sensitive isolates. Results The isolation rate of resistant isolates in intensive care unit (ICU) was the highest-level, and the isolates were mainly isolated from sputum. The genotype types of carbapenem-resistant and -sensitive Acinetobacter baumannii were classified into 7 categories by REP-PCR. All the carbapenem-resistant isolates were type A. OXA-23 and OXA-51 were positive in 110 carbapenem-resistant isolates. However, OXA-24, OXA-58, IMP-1, IMP-2, VIM-1 and VIM-2 could not be detected in all the isolates. The positive rates of the efflux pump-encoding genes (adeA, adeB, adeC, adeJ and adeG) were 100%. The expression level of efflux pump-encoding genes (adeA, adeB, adeC) in resistant isolates was significantly higher than that in sensitive isolates. Conclusions The main popular type of carbapenem-resistant Acinetobacter baumannii is type A. Clinical staff should pay attention to this phenomenon. The expression of OXA-23 and OXA-51 overexpression of adeA, adeB and adeC efflux pump-encoding gene may play an important role in carbapenem-resistant Acinetobacter baumannii.

Key words: Acinetobacter baumannii, beta-lactamase, Efflux pump, Repetitive-sequence polymerase chain reaction, Real-time fluorescence quantitation polymerase chain reaction

CLC Number: