Analysis Of Antibiotic Resistance And Study Of Resistance Mechanisms On Carbapenem-resistant Acinetobacter Baumannii

Objective: The drug resistance of Acinetobacter baumannii was more and more serious,presenting the multiple drug resistance,extensively drug resistance and pan-drug resistance.Investigated and analyzed the distribution characteristics,drug resistance and the production of carbapenemases in the clinical strains in the Hongqiao Hospital of Tianjin and understood the relationship between Acinetobacter baumannii and carbapenemases,integration,inserted sequence common area,complexity of integron,overexpression of efflux pump,membrane protein loss.Methods: A total of 47 non-duplicate imipenem-resistant and meropenem-resistant Acinetobacter baumannii were collected from the Hongqiao Hospital of Tianjin from January 2014 to August 2017;The carbapenemases were screened by the Modified Hodge test(MHT),EDTA synergy test and the Carbapenem Inactivation Method(CIM);All isolates were amplified by PCR for targeting genes encoding for class A genotype bla KPC,class B metallo-?-lactamases genotyp bla IMP-1,bla VIM-2,bla NDM-1,class D bla OXA-23-like,bla OXA-24-like,bla OXA-51-like,bla OXA-58-like and ISAbal inserted sequence of the bla OXA-23 and bla OXA-51 gene upstream;Integrase gene Int1 and Int2 were amplified by PCR;Isolates harboring class I integrase genes were further investigated by PCR and the variable regions were sequenced,the drug resistance gene cassettes were analyzed;The ISCR1 gene was amplified by PCR and the variable regions were sequenced,the drug resistance gene cassettes were analyzed;the resistance gene cassettes were analyzed for the strains containing class I integron and ISCRl;Efflux pump gene ade A,ade B,ade C,ade S,ade R and membrane protein gene car O were amplified by PCR;SPSS17.0 software was applied to analyze the variance of antibacterial drugs for integron and ISCR1 positive and negative strains;Variance analysis were performed on the positive rates of the efflux pump gene ade A,ade B,ade C,ade S and ade R of CRAB and CSAB.Results: 47 strains of carbapene-resistant Acinetobacter baumannii were mainly derived from sputum specimens of respiratory tract,mainly in ICU,followed by respiratory medicine;The phenotype screening results were positive for 8 strains in the Modified Hodge test,1 strain in the CIM and the results were all negative by the EDTA test;The results of carbapenemases genes were all not detected in class A and B,all of which were positive in the type D bla OXA-51 and bla OXA-23 genotypes;bla OXA-23 gene of 46 strains were on the upstream of insertion sequence ISAbal;14 strains of the integron-positive strains owned the variable area;PCR amplification and sequencing revealed that 14 integron-positive Acinetobacter baumannii isolates contained a 2000 bp gene cassette array with aac A4,a 3000 bp gene cassette array with aac C1;7 strains owned the variable region for 19 strains of ISCR1,about 2000 bp,the presence of gene tnp A was confirmed by sequencing;The variable regions for 4 strains owning Int1 and ISCR1 were positive and consistent with the target gene 2027 bp and the gene cassettes were confirmed by sequencing with bla IMP-18,aad A1 b,bla OXA-2 and qac ED1;The gene results of efflux pump were for 44 strains of ade A,44 of ade B,43 of ade C,44 of ade S and 44 of ade R,respectively;The efflux pump genes in CRAB were significantly higher than that in CSAB,P<0.05,the difference was statistically significant;The membrane protein genes of car O were positive for 43 strains,lack of genes for 4 strains.Conclusion: ICU and respiratory medicine were the key monitoring departments in the Hongqiao Hospital of Tianjin;The bacteria resistance was very serious to 21 kinds of antimicrobial drugs,and only amikacin remained relatively high sensitive;Production of bla OXA-23 and bla OXA-51 carbapenemase in Acinetobacter baumannii were major mechanisms of carbapenems resistance in our hospital;As a promoter,ISAbal regulated the expression of bla OXA-23 genes,resulting in resistance to many kinds of antimicrobial drugs;I class integrators mainly mediated aminoglycoside resistance;ISCR1 mediated various antimicrobial drug resistance;Class I integrons and ISCR1 can exist in series form,forming complex integrators,which mainly mediate ?-lactamase,aminoglycoside and quaternary ammonium salts;The gene carrying rates of the efflux pump were very high,which played an important role in bacterial resistance;The loss of membrane protein gene was not effective in the mechanism of Acinetobacter baumannii in our hospital.