Identification of a plasmid-borne blaIMP-11 gene in clinical isolates of Escherichia coli and Klebsiella pneumoniae.

The acquired metallo-β-lactamases represent a significant clinical threat due to their unrivalled hydrolysis spectrum and their resistance to therapeutic inhibitors of β-lactamase. In this study, we identified plasmid- and integron-borne bla(IMP-11) in clinical isolates of Escherichia coli and Klebsiella pneumoniae. The bla(IMP-11) gene cassette was carried by a typical class 1 integron together with aacA1 and orfG gene cassettes. The integron, intI1-bla(IMP-11)-aacA1-orfG-qacEΔ1-sul1, was easily transferred by intraspecies and intergenus conjugation of bacteria, indicating that the integron is located on a transferable plasmid. The integrated genes were preceded by TGGACA-N(17)-TAAACT, a hybrid P(c) promoter. Similar to the wild-type donors, the transconjugants also showed reduced susceptibility or resistance to carbapenems, amikacin and kanamycin. The identical integron was detected in four bacterial strains which were genetically different but were isolated from infant inpatients in the same paediatric department. These results demonstrate the colonization of the plasmid- and integron-borne bla(IMP-11) and aacA1 in the hospital environment, highlighting the importance of surveying and controlling the spread of such resistance determinants in nosocomial pathogens.