Carbapenemases And Homology Of Carbapenem-resistant Acinetobacter Baumannii Isolates In Kunshan

Objective：To investigate the antibiotic resistance and distribution feature among clinicalAcinetobacter baumannii(AB)strains isolated from in this area to offer reliable evidenceto control and treat the infection of AB. Carbapenemases were screened byImipenem-EDTA double disk test and Modified Hodge Test. Carbapenemases geneswere detected by Polymerase chain reaction (PCR), to survey Carbapenem-resistantAcinetobacter baumannii(CRAB) resistance genes distribution in the region, provedinga theoretical basis for the treatment of CRAB infection and the control of the epidemicoutbreak. To study the homology of the pan-drug resistant Acinetobacterbaumannii(PDR-AB)by randomly amplified polymorphic DNA(RAPD)to guide thecontrol of the nosocomial infection and epidemiology investigation.Methods：1. Non-repetitive174strains of Acinetobacter baumannii were separated fromJanuary2010to December2012from a hospital local area were re-identified with theuse of API-20NE.2. Disk diffusion test was used to study the antimicrobial agents resistance ofAcinetobacter baumannii and transition of drug resistance. The results were evaluatedbased on Clinical and Laboratory Standards Institute (CLSI).3. The metallo-β-lactamase(MBL)-producers were detected by comparing theinhibition zones using imipenem containing EDTA or not in the MH agar.Carbapenemases were screened by modified Hodge test(MHT).4. The carbapenemases genotype of OXA-23, OXA-24, OXA-51, OXA-58IMP-1,VIM-1were performed with specific primers by polymerase chain reaction (PCR),thePCR products were purified and sequenced and we compared the sequences with the gene bank, which help us to understand its distribution character among multi-drugresistant Acinetobacter baumannii and analysis the gene cassettes coding multi-drugresistance and its corresponding resistance phenotype. The homology of these strainswere studied by Random Amplified Polymorphic DNA (RAPD-PCR) to make surewhether there was a outbreak by cross-infection among patients or wards.Results:1. The174strains of Acinetobacter baumannii were mainly sampled fromsputum taken from the intensive care unit (ICU) wards and department ofrespiratory,the same as the multi-drug resistance and pan-drug resistance strains. Theantimicrobial susceptibility results showed the drug resistance rate of AB to the13antibiotics were higher than50%in addition to the Cefoperazone/sulbactam, themulti-drug resistance situation of AB was serious in this area.2. A total of70strains imipenem or meropenem drug-resistace AB werecollected,10of which were positive by tested with EDTA double pieces efficiency testand68strains were positive to MHT. All strains produced carbapenemases which wereconfirmed as OXA-51by PCR, IMP-1gene was identified in8strains, OXA-23in66strains. OXA-24, OXA-58and VIM-1gene was not identified by PCR amplification.3.70strains of CRAB were divided into8RAPD profiles, the main genotypingresults were34strains had the same profiles(genotype‘A’),8strains (genotype‘B’)and9(genotype‘C’).conclusions:1. The drug resistance situation of AB was serious, which should be paid moreattention. Doctors should choose proper antibiotic drugs for different departments basedon antimicrobial susceptibility results. Infection monitoring should be enhanced in thearea to reduce the spread of drug-resistance bacteria.2. The coexistence of several resistance genes (OXA-51,OXA-23,IMP-1)contributes to the resistance to antimicrobial agents in Acinetobacter baumannii in thelocal.3. The result of RAPD analysis showed there were high homology inCarbapenem-resistant Acinetobacter baumannii strains, the spread of resistance clonesplays an important role in the trend of imipenem resistance. Because of high resistance rate of drugs especially carbapenems and prevalence of cloning strains, it is necessary tostrengthen the clinic monitoring to prevent and control the clinical infection ofAcinetobacter baumannii.