Complete sequencing of the bla(NDM-1)-positive IncA/C plasmid from Escherichia coli ST38 isolate suggests a possible origin from plant pathogens

The complete sequence of the plasmid pNDM-1_Dok01 carrying New Delhi metallo-β-lactamase (NDM-1) was determined by whole genome shotgun sequencing using Escherichia coli strain NDM-1_Dok01 (multilocus sequence typing type: ST38) and the transconjugant E. coli DH10B. The plasmid is an IncA/C incompatibility type composed of 225 predicted coding sequences in 195.5 kb and partially shares a sequence with bla(CMY-2)-positive IncA/C plasmids such as E. coli AR060302 pAR060302 (166.5 kb) and Salmonella enterica serovar Newport pSN254 (176.4 kb). The bla(NDM-1) gene in pNDM-1_Dok01 is terminally flanked by two IS903 elements that are distinct from those of the other characterized NDM-1 plasmids, suggesting that the bla(NDM-1) gene has been broadly transposed, together with various mobile elements, as a cassette gene. The chaperonin groES and groEL genes were identified in the bla(NDM-1)-related composite transposon, and phylogenetic analysis and guanine-cytosine content (GC) percentage showed similarities to the homologs of plant pathogens such as Pseudoxanthomonas and Xanthomonas spp., implying that plant pathogens are the potential source of the bla(NDM-1) gene. The complete sequence of pNDM-1_Dok01 suggests that the bla(NDM-1) gene was acquired by a novel composite transposon on an extensively disseminated IncA/C plasmid and transferred to the E. coli ST38 isolate.     

Identification of New Delhi metallo-β-lactamase gene (NDM-1) from a clinical isolate of Acinetobacter junii in China

New Delhi metallo-β-lactamase-1 (NDM-1) is a novel type of metallo-β-lactamase (MBL) responsible for bacterial resistance to β-lactam antibiotics. Acinetobacter junii was previously shown to possess a MBL phenotype; however, the genes responsible for this phenotype were not identified. In this study, we reported the identification of NDM-1 gene in a clinical isolate of A. junii from a child patient in China, which was resistant to all β-lactams except aztreonam but sensitive to aminoglycosides and quinolones. The cloned NDM-1 gene contained an open reading frame of 813 bp and had a nucleotide sequence 99.9% identical (812/813) to reported NDM-1 genes carried by Acinetobacter baumannii , Enterococcus faecium , Escherichia coli , and Klebsiella pneumoniae . Recombinant NDM-1 protein was successfully expressed in E.?coli BL21, and antibiotic sensitivities of the NDM-1-producing E.?coli were largely similar to the A.?junii 1454 isolate. The findings of this study raise attention to the emergence and spread of NDM-1-carrying bacteria in China.     

泛耐药基因NDM-1在大肠杆菌中的克隆表达及耐药性检测

目的:构建bla(NDM-1)基因重组质粒,表达新德里金属β内酰胺酶1(NDM-1),并检测携带bla(NDM-1)基因重组质粒的大肠杆菌的耐药状况。方法:PCR扩增编码NDM-1的基因bla(NDM-1),构建表达载体pGEX4T-1-NDM-1,并转化至大肠杆菌,转化子经PCR后测序,以确认构建和转化成功;用Western印迹验证重组蛋白的表达;用药敏纸片法检测含重组质粒pGEX4T-1-NDM-1的大肠杆菌的耐药谱;用E-test法测定其最低抑菌浓度(MIC)。结果:PCR及测序结果显示载体构建和转化成功;含重组质粒pGEX4T-1-NDM-1的大肠杆菌在37℃时,经1 mmol/LIPTG诱导5 h后,SDS-PAGE可见目的条带;除对替加环素和粘菌素敏感外,该重组子对多种碳青霉烯类抗生素耐药,E-test检测其对亚胺培南的MIC为64μg/mL。结论:构建了含泛耐药基因bla(NDM-1)的重组质粒,转入大肠杆菌后表达了融合蛋白,并对多种碳青霉烯类抗生素耐药。为进一步研究bla(NDM-1)基因和蛋白的功能奠定了基础。     

Molecular cloning and biological characterization of the recA gene from Pseudomonas syringae.

We have identified a recombinant plasmid, pCUV8, from a cosmid library of Pseudomonas syringae genomic DNA which contains a functional analog of the Escherichia coli recA gene. The plasmid was initially identified by its ability to restore UV resistance to E. coli HB101. Quantitative analysis demonstrated that it restored both recombination proficiency and UV resistance to an E. coli recA deletion mutant. By these criteria, pCUV8 appears to contain the P. syringae recA gene. Several pathogenic and epiphytic strains of P. syringae, but not E. coli, showed sequence homology to pCUV8 under normal stringency.     

Complete sequence of virulence plasmid pEIB1 from the marine fish pathogen Vibrio anguillarum strain MVM425 and location of its replication region

AIMS: The aim of this study was to determine the whole DNA sequence of pEIB1, one pJM1-like virulence plasmid from Vibrio anguillarum MVM425 and locate the replication region. METHODS AND RESULTS: DNA sequence of virulence plasmid pEIB1 from V. anguillarum MVM425 was determined using the methods of restriction endonuclease digestion, subcloning, and primer walking. The whole nucleotide sequence of pEIB1 comprises 66,164 bp, encoding 44 open reading frames (>400 bp) containing the genes of DNA replication, biosynthesis and regulation of the siderophore anguibactin and transport of ferric-anguibactin complexes. With no demonstrated replication origin, the Sau3AI partial digested plasmid DNA fragments of pEIB1 were ligated into the BamHI-fragment containing the kanamycin-resistance gene (Kmr). For there is no effective transformation in V. anguillarum, the ligated DNA was first introduced into E. coli JM83, and the transfomants were selected for resistance to kanamycin. It was demonstrated with southern blotting and DNA sequencing that plasmid pEIB7 containing the Sau3AI DNA fragment of pEIB1 (from 12516 to 13957) has the ability to replicate in E. coli JM83 and V. anguillarum MVM425sh. The segregational stability of plasmid pEIB7 kept in 100 and 4% in E. coli JM83 and V. anguillarum MVM425sh respectively when the cells were cultured in 200th generation. In following experiments, we also found that plasmid pEIB7 replicated at a middle-copy number of 10-40 in JM83, while at a high-copy number of 100-300 in MVM425sh. Moreover, pEIB7 can survive in V. alginolyticus, another fish pathogenic. CONCLUSIONS: With the whole DNA sequence of pEIB1 determining, it was found that pEIB1 showed microheterogeneity in its restriction endonuclease patterns with pJM1 though their DNA sequences had slight difference. According to the complete DNA sequence of pEIB1, its replication region was located from 12516 to 13957. And this replication region is compatible to pUC18 (pMB1), pKA3 (pSC101) and p15A: caiE (p15A). SIGNIFICANCE AND IMPACT OF THE STUDY: The worldwide vibriosis marine pathogen V. anguillarum strains contain common virulence, pJM1-like plasmids, independent on the geographical source. The pEIB1 was the second common virulence plasmid, which sequence was determined. Its sequence is highly homologous to pJM1 as they both encode biosynthesis and regulation of the siderophore anguibactin and transport of ferric-anguibactin complexes. Some interesting features as in pJM1 were also identified, such as transposon-like structures. So it can be deferred that the whole DNA sequences of virulent plasmid pEIB1 will be great helpful to future revealing these V. anguillarum virulence-related genes derived during evolution from transposition events or horizontal transfer of genes potentially originating in other organisms. Another result, replication region of pEIB1 locating is the first report about replication of pJM1-like plasmid. This work will be useful for researching pJM1-like plasmid replication mechanism in V. anguillarum.     

Structural and functional stability of IncP plasmids during stepwise transmission by trans-kingdom mating: promiscuous conjugation of Escherichia coli and Saccharomyces cerevisiae

In order to establish a gene transfer system for yeast by promiscuous conjugation, we constructed plasmid pAY101 which contained an oriT sequence derived from RK2 (IncP) and the yeast TRP1 and ARS1 genes. A conjugation mixture consisted of yeast Saccharomyces cerevisiae, E. coli harboring pAY101, and E. coli carrying a helper plasmid with mob and tra. In the conjugation mixture a tryptophan-requiring yeast mutant (trp1) was converted to be prototrophic for tryptophan at a frequency of about 10(-5) to 10(-3) per recipient cell. This E. coli-yeast conjugation system required the mob, tra, oriT, TRP1 and ARS1 genes. The mob and tra genes were trans-acting elements as in an E. coli conjugation system. The mobilization was inhibited by nalidixic acid as in a typical bacterial conjugation. DNA analysis indicated that the plasmid pAY101 was transferred from E. coli to S. cerevisiae, and retained its original structure and function in yeast host cells.     

Characterization of an IncFII plasmid encoding NDM-1 from Escherichia coli ST131

Background

The current spread of the gene encoding the metallo-ß-lactamase NDM-1 in Enterobacteriaceae is linked to a variety of surrounding genetic structures and plasmid scaffolds.

Methodology

The whole sequence of plasmid pGUE-NDM carrying the bla _NDM-1 gene was determined by high-density pyrosequencing and a genomic comparative analysis with other bla _NDM-1-negative IncFII was performed.

Principal Findings

Plasmid pGUE-NDM replicating in Escherichia coli confers resistance to many antibiotic molecules including β-lactams, aminoglycosides, trimethoprim, and sulfonamides. It is 87,022 bp in-size and carries the two β-lactamase genes bla _NDM-1 and bla _OXA-1, together with three aminoglycoside resistance genes aacA4, aadA2, and aacC2. Comparative analysis of the multidrug resistance locus contained a module encompassing the bla _NDM-1 gene that is actually conserved among different structures identified in other enterobacterial isolates. This module was constituted by the bla _NDM-1 gene, a fragment of insertion sequence ISAba125 and a bleomycin resistance encoding gene.

Significance

This is the first characterized bla _NDM-1-carrying IncFII-type plasmid. Such association between the bla _NDM-1 gene and an IncFII-type plasmid backbone is extremely worrisome considering that this plasmid type is known to spread efficiently, as examplified with the worldwide dissemination of bla _CTX-M-15-borne IncFII plasmids.     

两株分离自鸡粪便费格森埃希菌的耐药性

【背景】费格森埃希菌(Escherichia fergusonii)是与大肠杆菌同属、近源的病原菌,目前耐药性鲜有报道。【目的】对在浙江省鸡粪便中分离到的2株费格森埃希菌EFCF053和EFCF056进行耐药性检测和分析。【方法】通过微量肉汤稀释法进行MIC测定,二代高通量测序获得全基因组序列,并通过ResFinder数据库预测获得性耐药基因。利用S1-PFGE和Southernblotting杂交进行质粒和耐药基因的确认。【结果】两种菌均对氨苄西林、庆大霉素、氟苯尼考、磺胺异噁唑、复方新诺明、四环素耐药,其中菌株EFCF056还对粘菌素、头孢噻呋、大观霉素、恩诺沙星、氧氟沙星耐药。预测到耐药基因β-内酰胺类blaTEM-1A、blaCTX-M-65、blaOXA-1、blaTEM-1B、blaCTX-M-55;氨基糖苷类aac(3)-IId、aph(3')-Ia、aph(3')-Ib、aph(6)-Id、rmtB、aac(6')-Ib-cr、aadA2;粘菌素mcr-1;喹诺酮类qnrS2、aac(6')-Ib-cr、oqxA、oqxB;磷霉素fosA3;大环内酯类mph(A);苯丙醇类catA1、floR、catB3;利福霉素ARR-3;磺胺类sul1、sul2、sul3、dfrA12、dfrA14;四环素类tet(A)。另外,含有mcr-1基因的质粒通过实验证实可发生接合转移。【结论】结果显示费格森埃希菌可能是重要耐药基因存储库,费格森埃希菌与大肠埃希菌要在抗药性流行病学中加以区分,深入研究其MIC频率分布、重要耐药基因mcr-1及ESBL等,保障临床检测的准确性。     

Conditionally lethal genes in the N pilus region of plasmid pCU1.

Plasmid genes or regions that are conditionally lethal to Escherichia coli have been called kil and those lethal to Klebsiella but not to E. coli have been called kik. Both classes of genes are found in or close to the N pilus region of the plasmid pCU1 and the closely related plasmid pKM101. Here we describe two new and overlapping lethal genes that are located between kikA and traA of the plasmid pCU1 and display host specificity. KilC is lethal in E. coli and Klebsiella while kikC is lethal only in Klebsiella. The previously identified korA gene is sufficient to override the lethality of kilC in trans or in cis but is insufficient to override kikC. kilC expression in E. coli leads to cell death accompanied by an increase in average cell length without affecting septum formation.     

Self-transmissible plasmid in Zymomonas mobilis carrying antibiotic resistance.

The cryptic plasmid pRUT41 from Zymomonas mobilis was examined for its biological properties. This plasmid was found to be conjugally transferred from Z. mobilis CP4 to Escherichia coli BM21 and to carry genes for antibiotic resistance (gentamicin, kanamycin, and streptomycin). Covalently closed circular plasmid DNA was isolated from eight transconjugants of E. coli BM21. These plasmids were identical in mobility on agarose gels and exhibited the same restriction patterns as the native pRUT41 plasmid isolated from Z. mobilis. The plasmid location of the antibiotic resistance genes was further confirmed by transforming E. coli BM21 with isolated pRUT41 plasmid from strain CP4 and with plasmids from the transconjugants of BM21. Resistance to streptomycin, kanamycin, and gentamicin was tightly linked and transferred together in all cases.     

Self-transmissible plasmid in Zymomonas mobilis carrying antibiotic resistance

The cryptic plasmid pRUT41 from Zymomonas mobilis was examined for its biological properties. This plasmid was found to be conjugally transferred from Z. mobilis CP4 to Escherichia coli BM21 and to carry genes for antibiotic resistance (gentamicin, kanamycin, and streptomycin). Covalently closed circular plasmid DNA was isolated from eight transconjugants of E. coli BM21. These plasmids were identical in mobility on agarose gels and exhibited the same restriction patterns as the native pRUT41 plasmid isolated from Z. mobilis. The plasmid location of the antibiotic resistance genes was further confirmed by transforming E. coli BM21 with isolated pRUT41 plasmid from strain CP4 and with plasmids from the transconjugants of BM21. Resistance to streptomycin, kanamycin, and gentamicin was tightly linked and transferred together in all cases.     

Cloning and sequencing of the 7 alpha-hydroxysteroid dehydrogenase gene from Escherichia coli HB101 and characterization of the expressed enzyme.

The 7 alpha-hydroxysteroid dehydrogenase (EC 1.1.1.159) gene from Escherichia coli HB101 was cloned and expressed in E. coli DH1. The hybrid plasmid pSD1, with a 2.8-kbp insert of chromosomal DNA at the BamHI site of pBR322, was subcloned into pUC19 to construct plasmid pSD3. The entire nucleotide sequence of an inserted PstI-BamHI fragment of plasmid pSD3 was determined by the dideoxy chain-termination method. Within this sequence, the mature enzyme protein-encoding sequence was found to start at a GTG initiation codon and to comprise 765 bp, as judged by comparison with the protein sequence. The deduced amino acid sequence of the enzyme indicated that the molecular weight is 26,778. The transformant of E. coli DH1 harboring pSD3 with a 1.8-kbp fragment showed about 200-fold-higher enzyme activity than the host. The enzyme was purified by a single chromatography step on DEAE-Toyopearl and obtained as crystals, with an activity yield of 39%. The purified enzyme was homogeneous, as judged by sodium dodecyl sulfate gel electrophoresis. The enzyme was most active at pH 8.5 and stable between pH 8 and 9. The enzyme was NAD+ dependent and had a pI of 4.3. The molecular mass was estimated to be 120 kDa by the gel filtration method and 28 kDa by electrophoresis, indicating that the enzyme exists in a tetrameric form.     

Copy Number Change of the NDM-1 Sequence in a Multidrug-Resistant Klebsiella pneumoniae Clinical Isolate

The genetic features of the antimicrobial resistance of a multidrug resistant Klebsiella pneumoniae strain harboring bla _NDM-1 were investigated to increase our understanding of the evolution of NDM-1. The strain, KPX, came from a Taiwanese patient with a hospitalization history in New Delhi. Complete DNA sequencing was performed; and the genes responsible for antimicrobial resistance were systematically examined and isolated by library screening. KPX harbored two resistance plasmids, pKPX-1 and pKPX-2, which are 250-kb and 141-kb in size, respectively, with bla _NDM-1 present on pKPX-1. The plasmid pKPX-1 contained genes associated with the IncR and IncF groups, while pKPX-2 belonged to the IncF family. Each plasmid carried multiple antimicrobial resistance genetic determinants. The gene responsible for resistance to carbapenems was found on pKPX-1 and that for resistance to aztreonam was found on pKPX-2. To our surprise, we discovered that bla _NDM-1 exists on pKPX-1 as multiple copies in the form of tandem repeats. Amplification of bla _NDM-1 was found to occur by duplication of an 8.6-kb unit, with the copy number of the repeat varying from colony to colony. This repeat sequence is identical to that of the pNDM-MAR except for two base substitutions. The copy number of bla _NDM-1 of colonies under different conditions was assessed by Southern blotting and quantitative PCR. The bla _NDM-1 sequence was maintained in the presence of the antimicrobial selection; however, removal of antimicrobial selection led to the emergence of susceptible bacterial populations with a reduced copy number or even the complete loss of the bla _NDM-1 sequence. The dynamic nature of the NDM-1 sequence provides a strong argument for judicious use of the broad-spectrum antimicrobials in order to reduce the development and spread of antimicrobial resistance among pathogens.     

Plasmid-mediated conjugative transfer of Klebsiella sp. rcs genesable to induce colanic acid capsular polysaccharide biosynthesis in Escherichia coli

Regulation of capsular biosynthesis (rcs) genes, encoding the ability to induce the production of a colanic acid polysaccharide capsule, were transferred to Escherichia coli by conjugation with Klebsiella pneumoniae (aerogenes) of capsular serotype K36. Transfer was mediated by a 58.4-MDa conjugative plasmid of incompatibility group IncM, which carried a copy of Tn7 (specifying resistance to trimethoprim and streptomycin) together with determinants for several further resistances. This plasmid did not carry the rcs genes itself, but mediated the conjugative recA-dependent transfer of part of the Klebsiella chromosome to E. coli. Once resident in E. coli, the rcs gene(s) could not be mobilised to other strains of E. coli, and the mobilising plasmid could be cured from capsulate transconjugants without loss of the ability to produce colanic acid. All such cured transconjugants contained an insertion of Tn7 in the chromosome, suggesting that the transposon might be involved in mobilisation of the rcs genes from Klebsiella sp. to E. coli. These findings explain previous observations that the ability to manufacture capsular polysaccharide could be transferred by plasmids between Klebsiella sp. and E. coli.     

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

Background

Spread 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 Findings

The 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.

Conclusions

Although 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.     

Plasmid from photosynthetic bacterium Ectothiorhodospira Sp. carries a transposable streptomycin resistance gene

Centrifugation through a cesium chloride density gradient and agarose gel electrophoresis of the DNA from the purple non-sulfur photosynthetic bacterium Ectothiorhodospira sp. resolved a single extrachromosomal element, plasmid pDG1. Its size was estimated to be 13.2 kilobases by restriction endonuclease mapping. Plasmid pDG1 and two restriction fragments thereof were cloned in Escherichia coli C600 with plasmid pBR327 as a vector to form mixed plasmids pDGBR1, pDGBR2, and pDGBR3. The resistance to streptomycin and mercury found in Ectothiorhodospira sp. was transferred to E. coli C600 after transformation with pDGBR1 but not with pDGBR2 and pDGBR3. The replication origin of pDG1 was estimated to be within a 2-kilobase restriction fragment of pDG1 by monitoring its replication in E. coli HB101, using a kanamycin resistance reporter gene. High stringency molecular hybridization with 32P-labeled pDG1 identified specific fragments of genomic DNA, suggesting the integration of some plasmid sequences. In accordance with the hypothesis that this integration is due to a transposon, we tested the transfer of streptomycin resistance from pDG1 into plasmid pVK100 used as a target. For this test, we regrouped in the same cells of E. coli HB101, pDGBR1 and mobilizable plasmid pVK100 (tetr,kmr). We used the conjugation capacity of the pVK100/pRK2013 system to rescue the target plasmid pVK100 into nalidixic acid-resistant E. coli DH1. The transfer frequency of streptomycin resistance into pVK100 was 10(-5), compatible with a transposition event. In line with the existence of a transposon on pDG1, heteroduplex mapping indicated the presence of inverted repeats approximately 7.5 kb from one another.     

Evidence for the ability of L10 ribosomal proteins of Salmonella typhimurium and Klebsiella pneumoniae to regulate rplJL gene expression in Escherichia coli

Genes rplJ, coding for ribosomal protein L10 of Salmonella typhimurium and Klebsiella pneumoniae, have been cloned on pUC plasmid. The resultant multicopy recombinant plasmids were detrimental for the growth of normal JM101 E. coli host cells and harmless for the mutant JF3029 host. This negative effect is the evidence for the ability of heterologous L10 proteins to regulate expression of rplJL genes in E. coli. Nucleotide sequence was determined completely for S. typhimurium rplJL' DNA portion and partially for rplJL' genes of K. pneumoniae. According to the nucleotide sequence data obtained three amino acid substitutions differ L10 proteins of S. typhimurium and E. coli and the long range, providing for the coupled translations of L10 and L7/L12 cistrons in E. coli mRNA is also valid for S. typhimurium and K. pneumoniae.     

Identification and Characterization of the First Escherichia coli Strain Carrying NDM-1 Gene in China

New Delhi metallo-β-lactamase-1 (NDM-1), an acquired class B carbapenemase, is a significant clinical threat due to its extended hydrolysis of β-lactams including carbapenems. In this study, we identified the first confirmed clinical isolate of Escherichia coli BJ01 harboring bla _NDM-1 in China. The isolate is highly resistant to all tested antimicrobials except polymyxin. bla _NDM-1, bla _CTX-M-57, and bla _TEM-1 were identified in the isolate. bla _NDM-1 was transferable to E. coli EC600 and DH5α in both plasmid conjugation experiments and plasmid transformation tests. BJ01 was identified as a new sequence type, ST224, by multilocus sequence typing. Analysis of genetic environment shows complex transposon-like structures surrounding the bla _NDM-1 gene. Genetic analysis revealed that the region flanking bla _NDM-1 was very similar to previously identified NDM-positive Acinetobacter spp. isolated in China. The findings of this study raise attention to the emergence and spread of NDM-1-carrying Enterobacteriaceae in China.     

First Identification of Novel NDM Carbapenemase,NDM-7, in Escherichia coli in France

Background

The NDM-1 carbapenemase has been identified in 2008 in Enterobacteriaceae. Since then, several reports have emphasized its rapid dissemination throughout the world. The spread of NDM carbapenemases involve several bla _NDM gene variants associated with various plasmids among several Gram negative species.

Methodology

A multidrug-resistant E. coli isolate recovered from urine of a patient who had travelled to Burma has been characterized genetically and biochemically.

Principal Findings

E. coli COU was resistant to all antibiotics tested except amikacin, tigecycline, fosfomycin, and chloramphenicol. Analysis of the antibiotic resistance traits identified a metallo-ß-lactamase, a novel NDM variant, NDM-7. It differs from NDM-4 by a single amino acid substitution sharing an identical extended spectrum profile towards carbapenems. The bla _NDM-7 gene was located on an untypeable conjugative plasmid and associated with a close genetic background similar to those described among the bla _NDM-1 genes. The isolate also harbours bla _CTXM-15 and bla _OXA-1 genes and belonged to ST167.

Significance

This study highlights that spread of NDM producers correspond to spread of multiple bla _NDM genes and clones and therefore will be difficult to control.