Complete Sequencing of pNDM-HK Encoding NDM-1 Carbapenemase from a Multidrug-Resistant Escherichia coli Strain Isolated in Hong Kong

Abstract

BackgroundThe emergence of plasmid-mediated carbapenemases, such as NDM-1 in Enterobacteriaceae is a major public health issue. Since they mediate resistance to virtually all β-lactam antibiotics and there is often co-resistance to other antibiotic classes, the therapeutic options for infections caused by these organisms are very limited.MethodologyWe characterized the first NDM-1 producing E. coli isolate recovered in Hong Kong. The plasmid encoding the metallo-β-lactamase gene was sequenced.Principal FindingsThe plasmid, pNDM-HK readily transferred to E. coli J53 at high frequencies. It belongs to the broad host range IncL/M incompatibility group and is 88803 bp in size. Sequence alignment showed that pNDM-HK has a 55 kb backbone which shared 97% homology with pEL60 originating from the plant pathogen, Erwina amylovora in Lebanon and a 28.9 kb variable region. The plasmid backbone includes the mucAB genes mediating ultraviolet light resistance. The 28.9 kb region has a composite transposon-like structure which includes intact or truncated genes associated with resistance to β-lactams (bla TEM-1, bla NDM-1, Δbla DHA-1), aminoglycosides (aacC2, armA), sulphonamides (sul1) and macrolides (mel, mph2). It also harbors the following mobile elements: IS26, ISCR1, tnpU, tnpAcp2, tnpD, ΔtnpATn1 and insL. Certain blocks within the 28.9 kb variable region had homology with the corresponding sequences in the widely disseminated plasmids, pCTX-M3, pMUR050 and pKP048 originating from bacteria in Poland in 1996, in Spain in 2002 and in China in 2006, respectively.SignificanceThe genetic support of NDM-1 gene suggests that it has evolved through complex pathways. The association with broad host range plasmid and multiple mobile genetic elements explain its observed horizontal mobility in multiple bacterial taxa.

Macrolide resistance mechanisms inEnterobacteriaceae: Focus on azithromycin

“…Similarly to what has been described for the msr(D) gene, the msr(E) gene has been concomitantly reported with the mph(E) gene to be part of a common operon in both Gram-positive (Desmolaize et al, 2011b) and Gram-negative microorganisms, including E. coli, Salmonella enterica and C. freundii (Dolejska et al, 2013;Du et al, 2012;Gołebiewski et al, 2007;Gonz alez-Zorn et al, 2005;Ho et al, 2011) of different origins, including livestock. It is of note that the msr(E) gene is frequently referred to as the mel gene, while the mph(E) is indicated as the mph2 gene in most of the studies performed in Gram-negative microorganisms.…”

“…In this context, the acquisition and maintenance of a TMMR may be enhanced in an environment with a high presence of macrolides due to competitive advantages. Besides, indirect selection may also be made, because some TMMR are present in genetic structures that also include other antibiotic resistance determinants such as dfrA genes, involved in resistance to trimethoprim, aacA or aadA genes, involved in aminoglycoside resistance or b-lactamase genes, involved in b-lactam resistance, among others (Dolejska et al, 2013;Du et al, 2012;Ho et al, 2011;Pons et al, 2015;S aenz et al, 2010). Thus, the TMMR may be fixed in the bacterial genetic background by the use of unrelated antimicrobial agents, or by the presence of heavy metals or antibiotic traces in the environment as has been described in other cases (Stepanauskas et al, 2006;Vien et al, 2012).…”

“…As in the case of mef(A) and msr(D), it seems that the presence of the mph(E) gene, has a modest role in the development of macrolide-resistance, while strongly enhancing the pump out of some macrolides via the MsrE efflux pump (Desmolaize et al, 2011b). These two genes have frequently been described within plasmids surrounded by IS26 sequences as part of the Tn1548, which also carry other antimicrobial resistance determinants, such as ArmA, facilitating its dissemination (Dolejska et al, 2013;Du et al, 2012;Ho et al, 2011). The presence of truncated msr(E) genes has also been observed with the IS26 inserted within it (Granier et al, 2011).…”

Characterization of an rmtB-carrying IncI1 ST136 plasmid in avian Escherichia coli isolates from chickens

“…The DNA sequence analysis showed that there was a class 1 integron cassette array (intI1-dfrA12-orfF-aadA2-qacED1-sul1) and an insertion sequence ISCR1 on the downstream side of the rmtB gene in plasmid pEC008. Upstream of the rmtB gene, the structure bla TEM-1 -ISCfr1-aacC2-IS26 was found, which has also been reported in the IncL/M plasmid pCTX-M3, pNDM-HK and pEI1573, isolated from Citrobacter freundii, E. coli and Enterobacter cloacae, respectively (Gołebiewski et al, 2007;Ho et al, 2011;Partridge et al, 2012) (Fig. 1).…”

Characteristics and management of Enterobacteriaceae harboring IMP-4 or IMP-8 carbapenemase in a tertiary hospital

“…In 2010, a study to investigate the resistance mechanism of 49 Enterobacteriaceae isolates with decreased susceptibility to carbapenems collected at 16 teaching hospitals in China,confirmed the production of KPC-2, IMP-4 and IMP-8 carbapenemase 17 . In 2011, the first NDM-1 producing E. coli isolate was detected in Hong Kong 18 .Here we report the emergence of Enterobacteriaceae harboring IMP-4 or IMP-8 carbapenemases in a Chinese tertiary care hospital. This report describes the emergence, the infection control measures implemented, and the results of molecular investigations.…”