The Research Of The Mechanism Of Integron Mediated Drug-resistance In ESBLs-producing Strains

ObjectiveTo identify the categories and gene cassettes arrangements of integrons, and their distributions in extended spectrum beta-lactamases (ESBLs)-producing E.coli and K. pneumoniae and investigate integron-mediated multidrug resistance of ESBLs-producing strains in clinic. The flanking sequences of classⅠintegron were investigated using reverse PCR.MethodsFrom June 2009 to December 2009,100 strains of extended spectrum beta-lactamases (ESBLs)-producing E.coli and K. pneumoniae were isolated from Third Xiangya Hospital of Central South University. PCR was used to detect the presence of integrons and the genes coding for blaTEM, blaSHV and blaCTX-M, amplify the variable region, PCR-RFLP to screen the homology of integron variable region, and the gene cassettes were detected by DNA sequencing. Genomic DNA was digested by HindⅢrestriction enzyme and using reverse PCR investigated the flanking sequences of classⅠintegron.ResultsThe expression of classⅠintegron that was found among ESBLs-producing strains was 69%. Comparing to those without classⅠintegron expression, the strains with classⅠintegron presented significant higher resistance to 12 antibiotics (P＜0.05), including cephalosporin, quinolones, sulfonamides andβ-lactam/enzyme inhibitors. In the genes that coding for blaSHV, blaTEM and blaCTX-M,, the expressions of classⅠintegron were 84.4%,72.9% and 68.9%. Reverse PCR amplified 1800bp size class I fragment of integrase gene flanking sequences. ConclusionsThere was a good correlation between integron-carrying and the ESBLs-producing of E. coli and K. pneumoniae strains. Distribution of classⅠintegron in extend-spectrum beta-lactamases (ESBLs)-producing strains is prevalent. Class 1 integron harboring multi-drug resistance has been identified among E. coli and K. pneumoniae isolated. Class 1 integron has taken important part in multi-drug resistance. The results stressed the need for surveillance of the integron content of nosocomial E. coli and K. pneumoniae populations may be critical to predict and prevent the spread of particular antibiotic resistance determinants.