Drug Resistance And The β-lactamase Gene Taken By Acinetobacter Baumannii

ObjectiveAcinetobacter baumannii is an important clinical multidrug-resistant bacteria,which the separation rate second only to methicillin-resistant Staphylococcus aureus.In this study,we evaluated the distribution of multidrug-resistant A.baumannii carrying OXA genes in clinical departmens in our hospital,and we explored the mechanism of A.baumannii acquiring imipenem resistance.MethodsA total of 101 strains of multidrug-resistant A.baumannii were isolated from the clinical departmens in our hospital,and collected the complete treatment information of all patients.The bacterial resistant were analyzed by VITEK-2 Compact system and K-B method.The risk factors associated with multidrug-resistant A.baumannii infection were analyzed using patient treatment information.Another 160 strains of A.baumannii were collected including 80imipenem-resistant strains and 80 imipenem-sensitive strains.The OXA genes including bla OXA-23,bla OXA-24,bla OXA-51 and bla OXA-58 in A.baumannii were detected by multiple PCR method.4 strains of imipenem-resistant A.baumannii were randomly selected,and the bla OXA-23 gene were amplified by PCR method then ligated with shuttle vector p YMAb3 to construct expression vectors bla OXA-23/p YMAb3.The bla OXA-23/p YMAb3 vector transfected into A.baumannii(ATCC 17978)by electroporation.The positive clone was selected screened by kanamycin and meropenem,and then confirmed by RT-PCR assay.The resistant to imipenem of mutant when transfected with bla OXA-23/p YMAb3 vector was determined by dilution assay.ResultsThe widely-spreading multidrug-resistant A.baumannii in our hospital is a serious problem.We found the resistance rates of imipenem,ceftazidime,ceftriaxone and cefepime of A.baumannii originated from our hospital were reached to 100%,and the resistance rate of ciprofloxacin was 86.9%,and the resistance rate of cotrimoxazole was 85.0%,and the resistance rate of minocycline was 85.0%,and the resistance rate of tobramycin was 83.1%,and the resistance rate of levofloxacin was 56.3%,and the resistance rate of amikacin was 40.0%.The separation rate of multi-drug-resistant A.baumannii isolated in the ICU department was significantly higher than other departments.The patient’s time in ICU departments,the whole hospital stay time,the mechanical ventilation time,the central venous catheterization time,the indwelling catheter time,and the using of carbapenem antibiotics in the past one month were closely related to patients infected with multi-drug-resistant A.baumannii.All of multidrug-resistant A.baumannii originated from our hospital were carrying bla OXA-23 gene.The imipenem resistance of A.baumannii when transfected with bla OXA-23/p YMAb3 vector was improved 64 times,and its MIC reach to 32 μg/m L.ConclusionsA.baumannii in our hospital was highly resistant to commonly used antibiotics such as imipenem,especially in the ICU department.Tigecycline is still the most effective treatment drug at present.The time of staying in ICU and in hospital,mechanical ventilation time,central venous catheterization time,indwelling catheter time,and the using of carbapenem antibiotics in one month ago were closely related to the infection of multi-drug resistant A.baumannii.The shuttle vector p YMAb3 can stably express foreign genes in A.baumannii,and is a reliable tool for the study of important functional genes of A.baumannii.The bla OXA-23 gene was the main reason that induces the resistance of A.baumannii to imipenem in our hospital.In clinical work,great attention should be paid to the horizontal transmission of this gene,which caused the outbreak of multi-drug resistant A.baumannii in the hospital.