| Objective:The study aims to to research the mechanism of drug resistance of Acinetobacterbaumannii isolated from82inpatients at the First Hospital of Jilin University,investigate the antibiotic resistance and molecular support of resistance to β-lactams,aminoglycosides and fluoroquinolones in82strains of Acinetobacter baumanniiand provide reference basis for the future clinical medication.Methods:1. From January2011to May2014a total of82non-repetitive Acinetobacterbaumannii strains were collected from clinical specimens of aseptic humoral isolatedfrom82inpatients at the First Hospital of Jilin University. Bacterial identification andsusceptibility tests of Acinetobacter baumannii were performed by phoenixTM-100automatic identification and susceptibility analyzer. Cefoperazone sulbactam wasdetermined using the Kirby-Bauer disk diffusion methods.2. Drug resistance determinants including β-lactams resistance determininggenes (blaOXA-51, blaOXA-23, blaTEM, blaSHV, blaIMP, blaVIM), aminoglycoside-modifyingenzymes encoding genes (aac(6′)-I, aac(3′)-I, ant(3″)-I, ant(2″)-I), quinoloneresistance genes (gyrA, parC), class1integrase gene (intI1) and outer membraneprotein encoding gene (CarO) were detected by polymerase chain reaction (PCR),observe in the gel imaging system after1.5%agarose gel electrophoresis.3. All of the PCR products of gyrA and parC genes were digested with HinfIenzyme, observe in the gel imaging system after2%agarose gel electrophoresis andrandomly select part of the resistant strains and sensitive strains for sequencinganalysis to verify the results of drug susceptibility tests.Results:1. Antimicrobial susceptibility tests:65multi-drug resistant Acinetobacter baumannii (MDRAB) strains were detected. All of the82strains of Acinetobacterbaumannii were sensitive to polymyxin. Drug susceptible rate to imipenem,meropenem and cefoperazone sulbactam were41.5%,40.2%and29.3%, respectively.The susceptible rates of the other drugs except amikacin, tetracycline and bactrimwere less than20%.2. Detection of drug-resistance genes: blaOXA-51, gyrA and parC genes could bedetected in all strains of Acinetobacter baumannii. The positive incidence of blaOXA-23,intI1, blaTEM, aac(6′)-I, aac(3′)-I, ant(3″)-I, ant(2″)-I and CarO were52.4%,73.2%,70.7%,56.1%,56.1%,65.9%,12.2%and90.2%, respectively. blaSHV, blaIMPandblaVIMgenes could not be detected.3. Results of enzyme digestion: Only14(17.1%) amplification products of gyrAgene and23(28.0%) amplification products of parC gene could be digested by HinfIrestriction enzyme. DNA sequencing indicated that there were point mutations inquinolones resistant strains, classical mutations at Ser83to Leu in gyrA gene andSer80to Leu in parC gene were detected, novel mutations at Glu84to Gly in parCgene were also revealed, which was different from the traditional mutation at Glu84toLys.Conclusion:1. The current status of resistance to routine antibiotics among Acinetobacterbaumannii strains isolated from clinical is of great concern, most of the isolates weremulti-drug resistant Acinetobacter baumannii. The susceptible rate of carbapenemswas the highest. Eleven of fourteen kinds of resistance determining genes could bedetected except for blaSHV, blaIMPand blaVIMgenes, there may be regional differences.2. Carrying the blaOXA-23genes may be ralated to carbapenems resistance.Production of the OXA-23, OXA-51and TEM enzymes may contribute to β-lactamsresistance among Acinetobacter baumannii in our hospital.3. aac(3)-I, aac(6′)-I and ant(3″)-I genes played a role in aminoglycosidesresistance, ant(2″)-I was not the major gene resulting in aminoglycoside resistance inour hospital. 4. High level resistance to quinolones is related to mutations in gyrA and parCgenes. gyrA genes played a greater role in quinolones resistance. Novel mutations atGlu84to Gly in parC gene were revealed, but whether they contributed to quinolonesresistance need further verification. |
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