Occurrence and characterization of multidrugresistant new delhi metallo-β-lactamase-1- producing bacteria isolated between 2003 and 2010 in Bangladesh

The purpose of this study was to screen for reduced susceptibility against imipenem and the presence of the New Delhi metallo-β-lactamase-1 (NDM-1) gene in a collection of Enterobacteriaceae (Escherichia coli, Shigella spp. and Klebsiella pneumoniae) from different surveillance studies between 2003 and 2010 at the International Centre for Diarrhoeal Disease Research, Bangladesh. None of the E. coli (n51789) and Shigella spp. (n590) isolated between 2009 and 2010 from stool samples was resistant or had intermediate susceptibility to imipenem. Among 127 extended-spectrum β-lactamase-producing strains isolated during 2003-2009, three Klebsiella pneumoniae isolates (2.4 %) were resistant to imipenem and were positive for blaNDM-1. All these NDM-1-producing strains were isolated in 2008 and were resistant to all antibiotics tested except for tigecycline and colistin. All three isolates were positive for blaOXA-1 group, blaCTX-M-1 group (blaCTX-M-15) and blaSHV genes, whilst two isolates were positive for 16S rRNA methylase (armA) and qnr (qnrB) genes. One isolate was positive for the blaCMY gene and one for the rmtB gene. The blaNDM-1 gene was located on a conjugative plasmid of ~23-24 MDa. The PFGE patterns of the isolates were different from each other. This study highlights the occurrence of NDM-1-producing organisms in Bangladesh in 2008. The clonal diversity of the isolates and the transferability of blaNDM-1 plasmids suggest a wider distribution of NDM-1- producing bacteria in Bangladesh.

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