Association of QnrB determinants and production of extended-spectrum beta-lactamases or plasmid-mediated AmpC beta-lactamases in clinical isolates of Klebsiella pneumoniae.

Clinical isolates of Escherichia coli and Klebsiella pneumoniae producing extended-spectrum beta-lactamases or plasmid-mediated AmpC beta-lactamases were screened for qnrA and qnrB genes. QnrB was present in 54 of 54 DHA-1-producing K. pneumoniae isolates and 10 of 45 SHV-12-producing ones, suggesting that the distribution of plasmids conferring resistance to extended-spectrum cephalosporins and quinolones in clinical isolates of K. pneumoniae is widespread.