Association of blaDHA-1 and qnrB genes carried by broad-host-range plasmids among isolates of Enterobacteriaceae at a Spanish hospital

A collection of 30 DHA-1-Enterobacteriaceae producers was examined for the presence of qnr genes. PCR-based replicon typing, plasmid profile and Southern hybridisation analyses revealed that all isolates co-harboured blaDHA-1 and qnrB genes on the same plasmid. All but one of these plasmids belonged to the L/M group. Genetic organization analyses of a randomly selected isolate revealed the co-localization of both genes on an IS26-composite transposon. As plasmids carrying both genes seem to have a high prevalence and a worldwide distribution, care should be taken when quinolones are used to treat infections caused by DHA-1 producers.