Molecular characterization of NDM-1 producing Enterobacteriaceae isolates in Singapore hospitals
Open Access
- 14 February 2012
- journal article
- Published by World Health Organization, Western Pacific Regional Office in Western Pacific Surveillance and Response Journal
- Vol. 3 (1), 19-25
- https://doi.org/10.5365/WPSAR.2011.2.4.010
Abstract
Objective: In this study, we molecularly characterized 12 NDM-1 producing clinical Enterobacteriaceae ( Klebsiella pneumoniae, Escherichia coli, Enterobacter cloacae ) isolates that were part of a collection of non-carbapenem susceptible isolates obtained during a one-year period. These isolates were obtained from four local general hospitals in Singapore. Methods: Polymerase chain reaction (PCR) assays and sequencing was used to determine the presence of β-lactamase encoding genes ( bla ) including bla NDM-1 and plasmid-mediated quinolone and aminoglycoside resistance determinants. Conjugation experiments were performed to determine the transferability of bla NDM-1 . Isolate relatedness was determined by multilocus sequence typing (MLST). Results: The isolates were completely resistant to the second- and third-generation cephalosporins tested as well as carbapenems. Susceptibility profiling of the isolates indicated that 100% retained susceptibility to tigecycline while 11/12 (91.7%) were susceptible to colistin. The bla NDM-1 gene was encoded on plasmids that were easily transferable. None of the patients had a travel history to countries where NDM-1 has been reported. The isolates appear clonally unrelated with MLST, revealing a diversity of clonal types among the Klebsiella pneumoniae and Escherichia coli isolates. Conclusion: The ease of NDM-1 plasmid transmissibility may help their dissemination among the Enterobacteriaceae. Although it appears that the isolates are clonally unrelated, epidemiological links cannot be fully excluded without further research.Keywords
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