Molecular surveillance and clinical outcomes of carbapenem-resistant Escherichia coli and Klebsiella pneumoniae infections.

BACKGROUND/PURPOSE The emergence of carbapenem-resistant Enterobacteriaceae (CRE) is a cause for great concern. The aim of this study was to evaluate antimicrobial susceptibility, mechanisms of carbapenem-resistance in two members of the Enterobacteriaceae family (Escherichia coli and Klebsiella pneumoniae), and clinical outcomes of their infections. METHODS The susceptibility tests of 16 E. coli and 60 K. pneumoniae isolates, collected from 2010 to 2011, were assessed. The minimal inhibitory concentrations of eight antimicrobial agents were assessed by the broth microdilution method according to the recommendations of the Clinical and Laboratory Standards Institute. The detection of beta-lactamase genes was performed by polymerase chain reaction. The genetic relatedness of these isolates was determined by pulsed-field gel electrophoresis (PFGE) fingerprinting. RESULTS The carbapenemase genes blaKPC-2 and blaOxA were detected in one and five K. pneumoniae isolates, respectively. The genetic combinations blaSHV-5-blaDHA and blaSHV-5-blaCTx-M-G9 were prevalent in 45% and 26.7% of 60 K. pneumoniae isolates, respectively. The susceptibility rates of 60 K. pneumoniae isolates to colistin and tigecycline were 58.3% and 50.0%, respectively. The 30-day mortality rates of the patients treated with carbapenem, colistin, or tigecycline were as high as 60.6%. Nine clusters of K. pneumoniae isolates were identified by PFGE fingerprinting. CONCLUSION The findings of carbapenemase genes in a few isolates and small clusters of CRE indicated the emerging problems in the hospital. The high mortality rates were observed in the patients treated by colistin and tigecycline, although they were the only alternative treatment options for CRE infections. Active surveillance and an effective infection control strategy should be implemented to control the spread of CRE infections.