Molecular characterization of NDM-1 producing Enterobacteriaceae isolates in Singapore hospitals

Authors

  • Jeanette Teo Department of Laboratory Medicine, National University Hospital, Singapore, 119074 Singapore.
  • Grace Ngan
  • Michelle Balm
  • Roland Jureen
  • Prabha Krishnan
  • Raymond Lin

DOI:

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 ?-lactamase encoding genes (bla) including blaNDM-1 and plasmid-mediated quinolone and aminoglycoside resistance determinants. Conjugation experiments were performed to determine the transferability of blaNDM-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 blaNDM-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.

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How to Cite

1.
Teo J, Ngan G, Balm M, Jureen R, Krishnan P, Lin R. Molecular characterization of NDM-1 producing Enterobacteriaceae isolates in Singapore hospitals. Western Pac Surveill Response J [Internet]. 2013 May 30 [cited 2026 Mar. 25];3(1). Available from: https://ojs.wpro.who.int/ojs/index.php/wpsar/article/view/137

Issue

Vol. 3 No. 1 (2012): January – March

Section

- Original Research

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