Study On The Mechanism Of Carbapenem Resistance In Acinetobacter Baumannii

Objective:The aim of this study is to investigate the mechanism of carbapenems resistancein Acinetobacter baumannii in nanchang.Methods:Nonduplicate carbapenem-resistant A.baumannii (CRAB) isolates collectedduring2012in Second Affiliated Hospital of Nanchang University,strains wereidentified by vitek-32automatic microbe analyzer, antimicrobial susceptibility testingby Kirby-Bauer method.AmpC enzyme was screened by three dimensionaltest,Metallo β-lactamases(MBLs) by EDTA synergy test.blaIMP-1、blaIMP-2、blaIMP-4、blaVIM-2、blaNDM-1、blaSIM-1、blaADC、blaOXA-23、blaOXA-24、blaOXA-51、blaOXA-58、carO、adeB、adeS、adeR、intI1and ISAba1genes wereamplified by PCR,the positive results were sequenced to identify the genotype．Results:A total of84clinical isolates of CRAB were collected from January toDecember2012. More than90％of84CRAB isolates were resistant to9of12antimicrobial agents tested,but the least resistant tocefoperazone-sulbactam(44.0％）,and all the strains were multiple drug-resistant.Among the84isolates,AmpC enzyme in83(98.8％) strains was detected,noMBLs-producing strain was found by synergy test. All strains had blaOXA-23,blaOXA-51and blaADC genes and one had blaOXA-58gene,while MBLs andblaOXA-24genes were all negative. The positive rates of adeB,adeS and adeR geneswere98.8％(83/84),81.0％(68/84) and67.9％(57/84). The carO gene was found inall isolates,class I intergase gene was detected in69isolates,each strain carriedISAba1. Conclusions:The drug resistance of CRAB is very severer in nanchang. Production ofOXA-23carbapenemase in A.baumannii is major mechanism of carbapenemsresistance in local area. AmpC enzyme, efflux pump AdeABC, class I integron andISAba1may be closely related to multidrug resistance of CRAB.