ObjectiveTo analyze the homology of Citrobacter freundii strains and detect multidrug resistant genes.MethodsThe minimum inhibition concentration was tested with standard agar dilution method and the the homology of C.freundii strains was measured with pulsed field gel electrophoresis (PFGE) and the PCR was used to perform the drug resistant genes such as β-lactamase,disappearing of outer membrane channel protein.ResultsThe four strains ( No.1,2,4,5 ) showed nineteen banding patterns with PFGE.PCR experiment showed that there were 2 strains (No.1,4) with blaCTX-M,3 strains (No.2,3,5 ) with blaDHA,1 strains(No.3) with blaACT/MIR,and 4 strains(No.1,2,4,5) with blaKPC-2.PCR analysis comfirmed that No.2 and No.4 disappearing of OmpF and No.3 disappearing both of OmpC and OmpF.The expression levels of the chromosomal ampC gene of No.3 isolates was 106.7 times higher than the negative isolates.ConclusionThere is high homology in carbapenem-resistant isolates and the mechanism of drug resistance is complex including blaKPC,AmpC,ESBLs,disappearing of outer membrane channel protein.The spreading of drug resistance result from above genes.

ISG15, the first ubiquitin-like molecule identified two decades ago, is encoded by interferon stimulated gene 15 ( ISG 15), where its robust expression can be induced by viral infections or interferon treatments. ISG 15 conjugate to other proteins as the ubiquitin and was found to be involved in innate immune response. However, the functions of ISG15 modification remained unclear. We cloned bovine ISG15(bisg15) into a prokaryotic expression vector pET28a( + ) with a His-tag to generate a soluble form of bISG15 fusion protein, and purified with Ni-NTA Sepharose chromatography. The purified protein was concentrated and used to immune Balb/c mice to raise the antiserum, which could specifically recognize bISG15 expressed in eukaryotic cells by Western blot analysis. The concentrated bISG15 protein and its antiserum were then used to establish an in vitro bISG15 modification system. Our studies have demonstrated that cellular proteins could be conjugated to bISG15 with this system.