Characterization of carbapenemase-producing Enterobacteriaceae in the West Midlands region of England: 2007-14

Abstract

Objectives: Carbapenemase-producing Enterobacteriaceae (CPE) have been increasingly reported in the UK since 2003. We analysed patient and isolate data for CPE confirmed by the national reference laboratory from laboratories in the West Midlands region fromNovember 2007 to December 2014. Methods: MICs were determined by BSAC agar dilution methodology and isolates exhibiting resistance to one or more carbapenems were screened for carbapenemase genes by PCR. Plasmid analyses were performed after electro-transformation of carbapenemase-encoding plasmids. WGS was performed on both transformants and clinical isolates. Patient data provided by the sending laboratories were reviewed. Results: During the study period, CPE (n=139) were submitted from13 laboratories in the West Midlands region, originating from 108 patients and including one environmental isolate. CPE submissions increased significantly from 2009 onwards. Isolates were predominantly Klebsiella pneumoniae (89/139) obtained from inpatients. WGS was performed on all clinical isolates and transformants. After deduplication 119 isolates and 96 transformants remained for analysis. Within these, four families of carbapenemase genes were identified: blaNDM (69/119), blaKPC (26/119), blaOXA-48-like (16/119) and blaVIM (7/119); one isolate carried both blaNDM and blaOXA-48- like. Isolates represented diverse STs and plasmid replicon types. Plasmid analyses identified plasmids of different replicon types encoding blaKPC, blaNDM and blaOXA-48-like genes, found across several species and STs. Conclusions: CPE have been reported increasingly in the West Midlands region over a 7 year period. blaNDM, blaKPC and blaOXA-48-like were the dominant carbapenemase genes and were found in a range of diverse genomic/ plasmid environments, highlighting their ability to mobilize across different plasmids, often impeding the detection of outbreaks.