[Molecular epidemiological characteristics of clinically isolated carbapenem-resistant Acinetobacter baumannii in Changsha].
OBJECTIVE
To survey antibiotic resistance of clinical isolates of Acinetobacter baumannii in Changsha and to investigate molecular epidemiological characteristics of carbapenem-resistant Acinetobacter baumannii.


METHODS
A total of 205 non-duplicated, clinical isolates of Acinetabacter baumannii from 10 general hospitals in Changsha were collected from March 2010 to December 2010. The K-B disk diffusion method was applied for the drug-susceptibility test; a modified, double-disk synergy test was used to detect metallo-β-lactamase (MBL), and a modified Hodge test was used for the screening of carbapenemase. PCR was used to amplify carbapenemase genes (including OXA-23, OXA-24, OXA-51, IMP-1, and VIM-2) and the positive products were sequenced. Enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) was used for DNA typing and test of homology.


RESULTS
Of the 18 antibiotics tested, 14 had a high rate of resistance (>50% of the isolates tested), with piperacillin the highest (80.5% of strains), and cefoperazone/sulbactam the lowest (2.5%). In total, 115 carbapenem-resistant Acinetobacter baumannii strains were confirmed, but their MBL phenotype and genes were all negative. Seventy-one positive strains were detected by the modified Hodge test, among which 64 strains were OXA-23-positive. All the 115 strains were positive for the amplification of the OXA-51 gene, and no strain was found which carried OXA-24 or OXA-58 gene. Seven genomic types were included in the 115 Acinetobacter baumannii. The major prevalence types were Type B ( 72 strains) and Type A (19 strains).


CONCLUSIONS
Multiple drug resistance of clinically isolated Acinetobacter baumannii is a serious problem in Changsha. Production of OXA-23 and OXA-51 carbapenemases is an important mechanism of resistance to carbapenem antibiotics, and there is prevalence of the same clones in these carbapenem-resistant strains.
Department of Clinical Laboratory, Central South University, Changsha, China.
Wei
W
Liang
Mingxiang
M
Zou
Jingmin
J
Wu
Guojun
G
Wu
Jun
J
Li
Qingya
Q
Dou
Wenen
W
Liu
D000151:Acinetobacter Infections / Q000453:epidemiology* / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D015780:Carbapenems / Q000494:pharmacology*; D002681:China / Q000453:epidemiology; D004269:DNA, Bacterial / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D006801:Humans; D017720:Molecular Epidemiology; D010878:Piperacillin / Q000494:pharmacology; D016133:Polymerase Chain Reaction / Q000379:methods
D015780:Carbapenems; D004269:DNA, Bacterial; D010878:Piperacillin