Abstract
Objective To investigate the prevalence and transmission mechanisms of plasmid-mediated blaoxa-23 resistance genes in Acinetobacter baumannii. Methods One hundred and one Acinetobacter baumannii were collected from Obstetrics and Gynecology Hospital of Fudan University and Renji Hospital Shanghai Jiaotong University School of Medicine. Antibiotic susceptibility of carbapenems were determined by standard agar dilution method. Molecular typing of Carbapenem-resistant Acinetobacter baumannii(CRAB) was performed by MLST. blaoxa-23、blaoxa-24、blaoxa-51、blaoxa-58、blaIMP-1、blaVIM-1/2 and blaAmp-C were analyzed by PCR. The analysis of blaoxa-23 transposons for carbapenems resistant A. baumannii isolates was also performed by PCR. Plasmid was analyzed by gel electrophoresis. Conjugation experiments were performed to determine the transferability of blaoxa-23. Results The antibiotic susceptibility tests showed the resistant rates to carbapenems were extremely high, and the ones of imipenem and meropenem were 64.4% and 69.3%. Fifty-six (53%) isolates were carbapenems-resistant A. baumannii. Main clone ST208 includes 28 isolates(50%) in CRAB. A total of the CRAB isolates harbored blaoxa-23 and blaoxa-51 (100%), 44 for blaIMP-1 (78.6%) and 54 for blaAmp-C (96.4%), while blaoxa-24, blaoxa-58 and blaVIM-1/2 was undetected. Two previously identified transposons (Tn2006 and Tn2008) was found in the isolates.Plasmid gel electrophoresis results showed that the isolates carried 2-4 plasmids and blaoxa-23 were transferable by plasmids. Conclusions There is high carbapenems resistance of A. baumannii infections. ST208 was the most prevalent molecular type. The mainly drug-resistant genes of A. baumannii are blaoxa-23. Based on the findings, blaoxa-23 is plasmid mediated, suggesting that it may transfer by plasmids carrying Tn2008 transposon, thus induced isolates resistant to carbapenemase. (Chin J Lab Med, 2017, 40: 36-40) Key words: Acinetobacter baumannii; Beta-Lactamases; Plasmids
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