Genotype And Molecular Epidemiology Of Carbapenem Resistant Acinetobacter Baumannii

Objective To investigate the characteristic of carbapenem resistant Acinetobacter baumannii,classⅠintegron gene, the carbapenem resistant genes and their relationship with ISAba1element.To study the homology of CRAB and to identify if there were such prevalence caused by drug-resistant strains of clones. Methods Microdilution method was used to test the sensitivity of39Acinetobacter baumannii resistant to carbapenem isolated from the affiliated hospital of NingboUniversity from June2009to June2010against13kinds of antibiotics. PCR and DNA sequencingwere used to identify the carbapenem resistant genes and their realationship with ISAbal andclassⅠintegron gene. Pulsed-field gel electrophoresis(PFGE) was used to detect homology of.Acinetobacter baumannii. Result39isolates were from12wards, the resistance rate of Amicakin,Polymyxin and Minocycline were5.1%,0%and0%respectively. The resistance rates of otherantibiotics were more than90%. Genes blaOXA-23-like and blaOXA-51-like were amplified from37and39isolates, respectively. Sequencing of blaOXA-51-like amplicons identified blaOXA-66,whereas blaOXA-23-like sequences were classical blaOXA-23. The blaOXA-23gene was located34bp downstream of ISAba1and blaOXA-66gene was located8bp downstream of ISAba1. All39isolates were positive for classⅠintegron genes and negative for genes blaOXA-24-like,blaOXA-58-like, blaIMP, blaVIM and blaSIM. All of39isolates belonged to three PFGEpulsotypes(A,B,C). Pulsotype A were20isolates(17of type A,1of subtype A1,1of subtype A2,1of subtype A3); Pulsotype B were18isolates(15of type B,2of subtype B1,1of subtype B2);1pulsotype C isolate. Conclusion Genes blaOXA-23and blaOXA-66may be the main resistancemechanism which caused Acinetobacter baumannii resistant to carbapenem in the affiliatedhospital of Ningbo University. The emergence of CRAB in this hospital is associated with thespread of Acinetobacter Baumannii strains of clone A and B.