Abstract

Plasmid-mediated resistance to quinolones in clinical isolates has been found. We have recently identified the types of the plasmid-mediated qnrB genes in Klebsiella pneumoniae, Escherichia coli and Citrobacter freundii. Through BLASTn analysis of qnrB alleles’ characteristics, we had obtained qnrB5 gene and qnrB31 gene (GenBank accession number HQ418999) in plasmids of isolates of K. pneumoniae, qnrB9 and qnrB16 genes in plasmids of isolates of E. coli, and qnrB2, qnrB15 and qnrB18 genes from C. freundii. And the susceptibility testing showed that the main causes of resistance to quinolone were mediated by plasmid. The analysis of the structure of qnrB alignment showed that LexA-protein-binding site was the determining gene of fluoroquinolone resistance, and if the gene exist then the strains were sensitive to fluoroquinolone and vice versa.
 

Key words: Quinolone-resistance, QnrB, Klebsiella pneumonia, Escherichia coli,Citrobacter freundii.