Characterization of KPC-2-Producing Escherichia coli, Citrobacter freundii, Enterobacter cloacae, Enterobacter aerogenes, and Klebsiella oxytoca Isolates from a Chinese hospital

摘要

Twelve nonduplicated KPC-2-producing enterobacterial isolates, including three Escherichia coli, two Citrobacter freundii, two Enterobacter cloacae, four Enterobacter aerogenes, and one Klebsiella oxytoca, were collected from various clinical samples within 18 months (March 2011 to September 2012). Two of the 12 patients died from infections caused by KPC-2-producing pathogens, while the rest of the patients with KPC-2-producing pathogens improved or were cured. The majority of the clinical isolates exhibited a high-level of resistance to oxyimino-cephalosporins and carbapenems, and possessed self-transferable blaKPC-2-carrying plasmids with sizes ranging from 20 to 120?kb. Most isolates carried blaCTX-M and plasmid-mediated quinolone resistance genes, while some isolates produced 16S rRNA methylases (ArmA or RmtB). The genetic environment of blaKPC-2 of most clinical strains was consistent with the genetic structure surrounding blaKPC-2 on the plasmid pKP048, which contains an integration structure of a Tn3-based transposon and partial Tn4401 segment. Inserted fragments (truncated bla TEM) were detected upstream of the blaKPC-2 gene for two E. aerogenes strains. In conclusion, the enterobacterial isolates exhibited sporadic emergence and did not arise by clonal spread at our hospital. The outcome of infections caused by KPC-producing enterobacterial isolates and their mortality were closely associated with the baseline condition of patients. The spread of blaKPC-2 gene between different enterobacterial species in China was mainly mediated by horizontal transfer of the Tn3-based transposons and not the blaKPC-2-carrying plasmids.