Study On The Mechanism Of Drug Resistance To Tigecycline In Acinetobacter Baumannii

Part? Analysis of drug resistance and homology of Acinetobacter baumanniiObjective Acinetobacter baumannii is one of the main opportunistic pathogen in clinical.and due to its increasing resistance to common clinical antibiotics,its monitoring of drug resistance has drawn more and more attention.Non-repetitive Acinetobacter baumannii isolated from our hospital was collected and tested for susceptibility and homology.In order to investigate the drug resistance of Acinetobacter baumannii,guide the clinical rational use of drugs and provide reference for the prevention and treatment of Acinetobacter baumannii infection in our hospital.Methods From 2014 to 2015,Acinetobacter baumannii was collected from the First Affiliated Hospital of Anhui Medical University,using the K-B(Kirby Bauer)method for drug sensitive test,applicating enterobacteriaceae intergenic repetitive sequence polymerase chain reaction(ERIC-PCR)for strains classification and DNA homology analysis.Results A total of 412 Acinetobacter baumannii strains were collected,of which 24 strains were resistant to tigecycline-resistant pan-drug-resistant Acinetobacter baumannii.Susceptibility results showed that Acinetobacter baumannii had the highest susceptibility to polymyxin B(98.8%),followed by tigecycline and minocycline(87.3% and 76.6% respectively);Amikacin and Cefoperazone/sulbactam was 62.5% and 37% respectively,and the other antibiotics showed different degrees of sensitivity.The 24 isolates of tigecycline-resistant Acinetobacter baumannii were classified into 4 types by ERIC-PCR,named genotype A,B,C and D.There mainly was B genotype,which accounted for 87.5%.Conclusion There has been clonal spread of Acinetobacter baumannii among patients in the hospital.The multidrug resistance rate of Acinetobacter baumannii is high,and the treatment is difficult.It poses a serious threat to the clinical antibacterial treatment.The prevention and control situation is still grim and more attention should be paid to resistance surveillance and rational use of antibiotics.Part? Mechanisms of tigecycline resistance in pandrug-resistant Acinetobacter baumannii strainsObjective Efflux pump systems and its control system are part of the most important mechanisms conferring in Acinetobacter baumannii.The RND family efflux pump is the most important efflux pump system for resistance to tigecycline in Acinetobacter baumannii.By detecting the expression of efflux pump in the pan-drug-resistant Acinetobacter baumannii,as well as the regulation of gene mutation,to explore pandrug-resistant Acinetobacter baumannii mechanism for tigecycline reduced susceptibility.Methods Twenty-four strains of pandrug-resistant Acinetobacter baumannii isolated were selected from the first part.Minimal inhibitory concentrations(MICs)of tigecycline against Acinetobacter baumannii strains were determined by broth microdilution method with or without efflux pump inhibitors of Phe-Arg-?-naphthylamide(PA?N).Polymerase chain reaction(PCR)was used to detect the carriage of ade A,ade B,ade C,ade G,abe J and two-component regulatory system genes ade RS,bae RS and other resistance genes tet X,tet Xl,trm and rps J.The expression levels of ade B,ade G and abe J were measured using quantitative real-time transcription-polymerase chain reaction(RT-PCR).Results In 24 strains of Acinetobacter baumannii,the detection rate of ade B gene was91.7%,the detection rate of ade G and abe J gene was 95.8%.The expression levels of ade B in drug-resistant strains were significantly higher than sensitive strains.The gene ade S found a site mutation,while the other regulatory genes ade R,bae R and bae S had no gene mutation or insertion sequence.No mutations were found in the trm and rps J resistance genes and none of the two genes including tet X and tet X1 were detected.Conclusion The efflux pump system Ade ABC may play a role in Acinetobacter baumannii resistant to tigecycline.The increase of their expression level is not caused by the gene mutations in the sequences of ade R,bae S and bae R or insert sequence,there may be other mechanisms.