Study On The Relationship Between The Mobile Genetic Elements And The Multi-drug Resistance Of Bacteria

Objective:To investigate the existence of the mobile genetic elements in the multi-drug resistant strains of Pseudomonas aeruginosa. Identify the impact of the different promoters on the integrated efficiency and the expression of the gene cassette in class1integron.Methods:49strains of multi-drug resistant Pseudomonas Aeruginosa were isolated from the clinical departments. Analyze the presence of21kinds of mobile genetic elements by polymerase chain reaction (PCR) Construct two plasmid containing highly expressed integrase and both non-gene-cassette integron and aadA2gene cassette, respectively, named pET-INT and pACYC-IN-AAD. Obtain the plasmid containing different variable region promoter by point mutation. The integrated frequency was measured by phenotypic screening and the expression level of aadA2and intll gene was detected by real-time quantitative PCR.Results:The49strains of PA were detected to carry11kinds of mobile genetic elements, among which the positive rate of IS26was the highest(77.6%), followed by intll (67%). It is the first time that the traF gene was detected in PA. In BL21(DE3), the integrated frequency of integron with high expression level of integrase is9.41-fold higher than the integron without it. The transcriptional level of aadA2gene that downstream of the strong Pant were about114folds higher than that downstream of the weak Pant, the most weak Promoter.Conclusions:The mobile genetic elements were existed extensively among PA. The Insertion Sequences and Integrons played an important role in the horizontal transfer of drug-resistant gene. The higher the start strength of the promoter, the stronger gene expression level of the gene cassette downstream. There are14pictures,14tables and42refrences.