Sequence of Closely Related Plasmids Encoding blaNDM-1 in Two Unrelated Klebsiella pneumoniae Isolates in Singapore

Abstract

BackgroundSpread of the bla NDM-1 gene that encodes the New Delhi metallo-β-lactamase (NDM-1) in Enterobacteriaceae is a major global health problem. Plasmids carrying bla NDM-1 from two different multi-drug resistant Klebsiella pneumonia isolates collected in Singapore were completely sequenced and compared to known plasmids carrying bla NDM-1.Methodology/Principal FindingsThe two plasmids, pTR3 and pTR4, were transferred to Escherichia coli recipient strain J53 and completely sequenced by a shotgun approach using 3-kb paired-end libraries on 454. Although the K. pneumoniae strains were unrelated by molecular typing using PFGE and MLST, complete sequencing revealed that pTR3 and pTR4 are identical. The plasmid sequence is similar to the E. coli NDM-1-encoding plasmid p271A, which was isolated in Australia from a patient returning from Bangladesh. The immediate regions of the bla NDM-1 gene in pTR3/4 are identical to that of p271A, but the backbone of our plasmid is much more similar to another IncN2 plasmid reported recently, pJIE137, which contained an additional 5.2-kb CUP (conserved upstream repeat) regulon region in comparison to p271A. A 257-bp element bounded by imperfect 39-bp inverted repeats (IR) and an incomplete version of this element flanking the 3.6-kb NDM-1-encoding region were identified in these plasmids and are likely to be the vestiges of an unknown IS.ConclusionsAlthough the hosts are not epidemiologically linked, we found that the plasmids bearing the bla NDM-1 gene are identical. Comparative analyses of the conserved NDM-1-encoding region among different plasmids from K. pneumoniae and E. coli suggested that the transposable elements and the two unknown IR-associated elements flanking the NDM-1-encoding region might have aided the spreading of this worrisome resistance determinant.

Genomic Characteristics of NDM-Producing Enterobacteriaceae Isolates in Australia and Their bla NDM Genetic Contexts

“…Genetic variations in the accessory regions of plasmids have contributed to the complexity that underlies the spread of antimicrobial resistance determinants between bacterial hosts. Since its first description (5), bla NDM has been reported on various plasmid Inc types (6), including IncA/C (7,8), IncF types (9), IncL/M (10), IncH (11), IncN types (12)(13)(14), IncX types (15), and IncHI1 types (16), of the family Enterobacteriaceae. However, it may be misleading to assume that all plasmids of the same replicon type are identical, especially among the IncA/C (7,(17)(18)(19) and IncFII (9,20) plasmids.…”

“…The bla NDM genetic contexts of NDM producers from Singapore, Japan, Hong Kong, Thailand, and Taiwan have been described (10,(12)(13)(14)18). Additionally, NDM-producing Enterobacteriaceae have been reported in Australia (27,28).…”

The genetic analysis of Enterobacteriaceae plasmids to provide insights into the acquisition and spread of the blaNDM gene

“…However, it may be misleading to assume that each plasmid of the same replicon type is identical, especially amongst the IncA/C (94,175,177,205) and IncFII plasmids (182,202 The blaNDM genetic context of NDM-producers from Singapore, Japan, Hong Kong, Thailand and Taiwan has been described (74,125,177,203,224). Additionally, NDM-producing…”

“…ASM authors also retain the right to reuse the full article in his/her dissertation or thesis. The blaNDM genetic context of NDM-producers from Singapore, Japan, Hong Kong, Thailand and Taiwan has been described (74,125,177,203,224). Additionally, NDM-producing…”

“…9). This is consistant with the different genera described to carry these plasmid sub-types (22,39,40,125,249,276).…”