Genetic environment of metallo-β-lactamase genes in Pseudomonas aeruginosa isolates from the UK

Objectives: We sought to characterize the genetic environment of bla(VIM) and bla(IMP) genes in Pseudomonas aeruginosa isolates from the UK; these included members of six previously described prevalent complexes, A-F, which correspond to international 'high-risk clones', along with diverse strains. Methods: Metallo-beta-lactamase (MBL)-encoding class 1 integrons were amplified by PCR from 218 P. aeruginosa isolates producing VIM-type (n = 196) or IMP-type (n = 22) enzymes, referred from UK hospital laboratories between 2003 and 2012. The variable regions of selected integrons were sequenced using a primer walking method. Results: One-hundred-and-nineteen isolates had an MBL-encoding integron with the 3' conserved sequence (3' CS), 65 had Tn5090-like 3' regions and 17 had the sul1 gene, but lacked the qacE Delta 1 gene; the 3' region could not be amplified using any primer combinations for the remaining 17 isolates. Six integron profiles were each seen in more than five isolates. Predominant integron types were seen amongst isolates belonging to STs 111, 233, 654/964 and 773 (complexes A, C, D and F, respectively), whereas diverse integron profiles were seen in isolates belonging to ST235 (complex B) and ST357 (complex E). Conclusions: In UK P. aeruginosa isolates, MBL genes occur in diverse class 1 integron structures, though commonly with 3' regions containing the classical 3' CS or Tn5090-like regions. Four of the six main clonal complexes, referred from multiple laboratories, carried a predominant integron type, whereas the remaining two had more diverse types.