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. 2017 Feb 23;61(3):e02347-16. doi: 10.1128/AAC.02347-16

High Incidence of Escherichia coli Strains Coharboring mcr-1 and blaNDM from Chickens

Bao-Tao Liu a,c,✉, Feng-Jing Song b, Ming Zou a, Qi-Di Zhang a, Hu Shan a,c
PMCID: PMC5328528  PMID: 28069644

ABSTRACT

This study investigated the characteristics of Escherichia coli isolates carrying mcr-1-blaNDM from a chicken farm in China. Of the 78 E. coli isolates, 21 clonally unrelated isolates carried mcr-1-blaNDM. Diverse IncI2 plasmids disseminated mcr-1, while the dissemination of blaNDM was mediated by diverse IncB/O plasmids. More striking was the colocalization of resistance genes mcr-1 and blaNDM-4 in an IncHI2/ST3 plasmid, which might pose a great challenge for public health.

KEYWORDS: high incidence, mcr-1, blaNDM, colocalization, Escherichia coli

TEXT

Carbapenems have been reliable and potent agents against Gram-negative bacteria. The rapid increase of carbapenem-resistant Enterobacteriaceae poses a great threat to public health and has prompted the reconsideration of colistin as a last-resort therapeutic option (1). Recently, a plasmid-borne colistin resistance gene (mcr-1) was identified in Escherichia coli and Klebsiella pneumoniae strains from animals and humans in China (2). This finding foreshadowed the inevitable dissemination of colistin resistance worldwide and was confirmed by the presence of mcr-1 in other countries (3–6).

The mcr-1 gene is often associated with the extended-spectrum β-lactamase gene and has been found with blaCTX-M in the same plasmid (4, 7, 8). The mcr-1 gene has also emerged in carbapenem-resistant isolates (4, 9, 10), and the cotransfer of mcr-1 and carbapenem resistance genes is obviously of great clinical concern. Recently, mcr-1 was even found with blaNDM in the same IncX3-X4 hybrid plasmid in E. coli from pets in China (11). However, only a few isolates resistant to both carbapenem and colistin were characterized in those previous studies.

Food-producing animals, especially chickens, serve as resistance gene “reservoirs,” so it is crucial to identify the origins of multidrug-resistant plasmids in these animals. In this study, we investigated the genetically diverse E. coli isolates carrying mcr-1 and blaNDM from a chicken farm and characterized the plasmids harboring mcr-1 or blaNDM.

Seventy-eight E. coli isolates were collected from diseased chickens in four separate barns on a large chicken farm (100,000 animals) in Shandong Province, China in October 2015. Feces from chickens that showed signs of diarrhea were randomly collected and streaked onto MacConkey agar. After incubating at 37°C for 20 h, one colony with typical E. coli morphology was selected from each chicken sample. Although detailed information on antibiotic usage was not available, ceftiofur and colistin were often used for prophylaxis and treatment of bacterial infections on this farm.

Susceptibilities to 18 antimicrobials were determined for these 78 isolates by the agar dilution method using the recommended breakpoints (12, 13). The colistin breakpoint (≥2 μg/ml) was used according to recommendations by the European Committee for Antimicrobial Susceptibility Testing.

Each of the 78 E. coli isolates was highly resistant to cefotaxime (100%), cefquinome (100%), and ampicillin (100%). The antimicrobial rates of resistance to other antibiotics were as follows: ceftiofur, 98.7%; doxycycline, 97.4%; tetracycline, 97.4%; nalidixic acid, 97.4%; kanamycin, 96.2%; florfenicol, 93.6%; enrofloxacin, 89.7%; ciprofloxacin, 83.3%; streptomycin, 83.3%; gentamicin, 78.2%; fosfomycin, 78.2%; levofloxacin, 74.4%; colistin, 73.1%; meropenem, 47.4%; and amikacin, 34.6%. Notably, 28 of the 37 meropenem-resistant isolates (75.7%) were resistant to colistin. Luckily, 18 isolates among the 28 meropenem-colistin-resistant isolates (64.3%) were sensitive to amikacin.

All 78 isolates were screened for the presence of mcr-1, blaNDM, and other carbapenemase genes using PCR typing as described previously (2, 14, 15). Subtyping of blaNDM was carried out using whole-gene sequencing of PCR amplicons. Thirty-four isolates (43.6%) carried blaNDM genes, and all were found in the 37 meropenem-resistant isolates. No carbapenemase genes were found in the remaining 3 meropenem-resistant isolates. Fifty-three isolates (67.9%) harbored the plasmid-borne colistin resistance gene, mcr-1. This rate of occurrence exceeds the 30% rate previously found in E. coli from chickens in 2014 in China (16), and may result from the use of colistin treatments on the farm in this study.

Twenty-one isolates carried both mcr-1 and blaNDM among the 28 meropenem-colistin-resistant isolates, and the incidence (26.9%; 21/78) of isolates carrying both genes in the chicken farm in this study was significantly higher than those from previous reports (9, 10). We also obtained 20 different pulsed-field gel electrophoresis (PFGE) patterns from these 21 isolates. This suggested that the high coincidence rate of mcr-1 and blaNDM in this study was not due to the clonal dissemination of blaNDM-mcr-1-positive isolates. Notably, isolate WF3-14 carrying blaNDM-1-mcr-1 and isolate WF3-21 carrying blaNDM-9-mcr-1 from the same chicken house had the same PFGE patterns (data not shown).

Multilocus sequence typing (MLST) (30) showed that the 21 isolates carrying mcr-1-blaNDM belonged to 10 distinct sequence types (STs). ST297 (5/21) and ST156 (5/21) were the most prevalent types. Two isolates each comprised ST2973, ST2847, and ST117. Single isolates represented groups ST101, ST617, ST10, ST1011, and ST2944. This result differs from those from previous studies in which E. coli isolates carrying mcr-1-blaNDM often belonged to ST167, which was not represented in our ST group (9, 17). The PFGE and MLST results indicated the severe situation of carbapenem and colistin resistance in China, especially in isolates from animals.

Isolates harboring blaNDM and mcr-1 were selected for conjugation experiments using the broth-mating method with E. coli C600 (streptomycin resistant) as the recipient (18). Transconjugants were selected on MacConkey agar plates containing streptomycin (2,000 μg/ml) and meropenem (0.8 μg/ml), or streptomycin (2,000 μg/ml) and colistin (2 μg/ml).

Of the 21 blaNDM-mcr-1-positive isolates, 12 transconjugants containing mcr-1 and 12 transconjugants carrying blaNDM were identified. Among the 12 blaNDM-positive transconjugants, 5 showed an additional resistance to fosfomycin and harbored fosA3 (Table 1). The most prevalent bla subtypes from the transconjugants were NDM-9 (7/12) and NDM-1 (3/12) (Table 1). The NDM-9 subtype was first identified on a 180-kb IncH plasmid from a clinical strain of Klebsiella pneumoniae in China, and it conferred higher levels of resistance to carbapenem than NDM-1 (19). Our results suggest that the NDM-9 allele has been an important subtype resulting in the high-level carbapenem resistance among Enterobacteriaceae in China.

TABLE 1.

Characteristics of E. coli transconjugants with plasmids harboring mcr-1 or blaNDM

Straina ST Gene detected
 MIC (μg/ml)b
 Other resistancesc Replicon type Size (kb)
mcr-1 blaNDM-1 blaNDM-4 blaNDM-5 blaNDM-9 blaCTXM1G (subtype) blaCTXM9G (subtype) floR fosA3 rmtB COL MEM CTX FOS
WF3-7 1011 + + + + 4 32 >128 4 AMP, CEQ, CIP, CTF, DOX, ENR, FFL, KAN, LEV, NAL, STR
    T1 + 0.125 32 >128 4 AMP, CEQ, CTF, STR B/O 340
    T2 + 4 0.125 0.06 4 STR I2 70d1
WF3-8 297 + + + + + 8 64 >128 >256 AMP, CEQ, CIP, CTF, DOX, ENR, FFL, GEN, KAN, LEV, NAL, STR, TET
    T1 + 0.25 64 >128 4 AMP, CEQ, CTF, STR B/O 140
    T2 + 8 0.125 0.125 4 STR I2 70
WF3-13 156 + + + + + 8 32 >128 >256 AMP, CEQ, CIP, CTF, DOX, ENR, FFL, GEN, KAN, LEV, NAL, STR, TET
    T1 + 0.25 32 >128 4 AMP, CEQ, CTF, GEN, KAN, STR B/O 167
    T2 + + 8 0.06 0.125 4 FFL, STR I2 70
WF3-14 156 + + + + + 4 8 >128 >256 AMP, CEQ, CIP, CTF, DOX, ENR, FFL, KAN, LEV, NAL, STR, TET
    T1 + + 0.25 8 >128 >256 AMP, CEQ, CTF, KAN, STR B/O 140
    T2 + + (55) 8 0.06 >128 4 AMP, CEQ, CTF, STR I2 70
WF3-21 156 + + + + + 16 32 >128 >256 AMP, CEQ, CIP, CTF, DOX, ENR, FFL, GEN, KAN, LEV, NAL, STR, TET
    T1 + + 0.125 32 >128 >256 AMP, CEQ, CTF, STR B/O 140
    T2 + + (55) 8 0.125 >128 4 AMP, CEQ, CTF, STR I2 70
WF3-26 10 + + + + + + 8 32 8 >256 AMP, CEQ, CIP, CTF, DOX, ENR, FFL, GEN, KAN, LEV, NAL, STR, TET
    T1 + 8 0.06 0.06 4 STR I2 70
WF3-27 156 + + + + + 4 8 >128 >256 AMP, CEQ, CIP, CTF, DOX, ENR, FFL, GEN, KAN, LEV, NAL, STR, TET
    T1 + + 0.25 8 >128 >256 AMP, CEQ, CTF, KAN, NAL, STR, TET B/O 140
WF3-41 156 + + + + + 8 32 >128 >256 AMP, CEQ, CIP, CTF, DOX, ENR, FFL, GEN, KAN, LEV, NAL, STR, TET
    T1 + 0.125 32 >128 4 AMP, CEQ, CTF, GEN, KAN, STR X3 100
WF5-3 297 + + + + + + 8 64 >128 >256 AMP, CEQ, CIP, CTF, DOX, ENR, FFL, GEN, KAN, LEV, NAL, STR, TET
    T1 + 0.25 64 >128 4 AMP, CEQ, GEN, CTF, STR B/O 173
    T2 + 2 0.25 0.125 2 STR I2 70d2
WF5-5 117 + + + + + + + 4 8 >128 >256 AMK, AMP, CEQ, CTF, DOX, FFL, GEN, KAN, NAL, STR, TET
    T1 + + + (14) + 4 8 >128 >256 AMP, CEQ, CTF, GEN, KAN, STR H12/ST3 400
WF5-18 297 + + + + + 8 64 >128 >256 AMP, CEQ, CIP, CTF, DOX, ENR, FFL, GEN, KAN, LEV, NAL, STR, TET
    T1 + + 0.25 64 >128 >256 AMP, CEQ, CTF, STR B/O 140
    T2 + 8 0.031 0.06 4 STR I2 70
WF5-23 2973 + + + + 8 8 >128 4 AMP, CEQ, CIP, CTF, ENR, FFL, GEN, KAN, LEV, NAL, STR, TET
    T1 + + 0. 25 8 >128 4 AMP, CEQ, CTF, FFL, STR B/O 140
    T2 + 8 0.06 0.125 4 STR I2 70d1
WF5-37 2973 + + + + + 8 32 >128 >256 AMP, CEQ, CIP, CTF, DOX, ENR, FFL, GEN, KAN, LEV, NAL, STR, TET
    T1 + 1 32 >128 4 CEQ, CTF, AMP, STR B/O 140
    T2 + 8 0.06 0.125 4 STR I2 70d2
WF5-38 101 + + + 8 8 >128 4 AMP, CEQ, CIP, CTF, DOX, ENR, FFL, GEN, KAN, LEV, NAL, STR, TET
    T1 + 8 0.031 0.125 4 STR I2 70
C600 0.25 0.031 0.06 4 STR
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a

T, transconjugant of above-listed parental strain.

b

COL, colistin; MEM, meropenem; CTX, cefotaxime; FOS, fosfomycin.

c

AMK, amikacin; AMP, ampicillin; CEQ, cefquinome; CIP, ciprofloxacin; CTF, ceftiofur; DOX, doxycycline; ENR, enrofloxacin; FFL, florfenicol; GEN, gentamicin; KAN, kanamycin; LEV, levofloxacin; NAL, nalidixic acid; STR, streptomycin; TET, tetracycline.

d

Restriction fragment length polymorphism patterns with same numbers (1 or 2) differ by only a few bands (n = 1–3).

The mcr-1-positive transconjugants showed 8- to 32-fold higher levels of colistin resistance than the recipient (Table 1). Two of these transconjugants (WF3-21-T2 and WF3-14-T2) showed high-level resistance to β-lactams drugs and carried blaCTX-M-55. The floR gene in WF3-13-T2 enabled florfenicol resistance in this strain. Notably, blaNDM-4 was cotransferred with mcr-1 in transconjugant WF5-5-T1, enabling resistance to meropenem and colistin. No other resistances were cotransferred with colistin resistance in 8 of the 12 mcr-1-positive transconjugants (Table 1).

Incompatibility (Inc) groups were assigned to each of the transconjugants by a PCR-based replicon typing method (20–22). The plasmid double-locus sequence typing (pDLST) for IncHI2 plasmids was performed as described previously (23). The location of blaNDM or mcr-1 in the transconjugants was analyzed by S1 nuclease-pulse-field gel electrophoresis (S1-PFGE) and Southern blotting. S1-PFGE revealed that 11/12 transconjugants carrying mcr-1 harbored only one ∼80-kb plasmid (Table 1 and Fig. 1). PCR-based replicon typing showed that all 11 plasmids of ∼80 kb belonged to the IncI2 type. These plasmids possessed mcr-1, and two of them contained mcr-1 and blaCTX-M-55 in WF3-14-T2 and WF3-21-T2 (Fig. 1 and Table 1). This result indicated that the dissemination of mcr-1 in the chicken farm in this study was mediated by IncI2 plasmids, consistent with the results from previous reports (6, 9, 24). To clarify whether a specific plasmid mediated the dissemination of mcr-1, the 11 IncI2 plasmids of ∼80 kb were digested with the endonuclease EcoRI (TaKaRa Biotechnology, Dalian, China). The two IncI2 plasmids from isolates WF5-3 (ST297) and WF5-37 (ST2973) and two from WF5-23 (ST2973) and WF3-7 (ST1011) had similar EcoRI restriction patterns. The remaining 7 isolates possessed ∼80-kb IncI2 plasmids with unique EcoRI digestion profiles, indicating a complex evolutionary process for these IncI2 plasmids carrying mcr-1.

FIG 1.

FIG 1

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Plasmid analysis of transconjugants carrying mcr-1 or blaNDM. (A) S1 nuclease-PFGE of transconjugants carrying blaNDM. (B) Southern blot hybridization with the blaNDM probe. (C) S1 nuclease-PFGE of transconjugants carrying mcr-1. (D) Southern blot hybridization with the mcr-1probe. Lanes 1 to 23: WF5-23-T1, WF3-27-T1, WF3-21-T1, WF3-7-T1, WF5-37-T1, WF3-8-T1, WF3-13-T1, WF3-41T1, WF5-18-T1, WF5-3-T1, WF3-14-T1, WF5-5-T1, WF5-18-T2, WF3-14-T2, WF3-13-T2, WF5-37-T2, WF3-7-T2, WF3-8-T2, WF5-3-T2, WF5-23-T2, WF3-21-T2, WF3-26-T1, WF5-38-T1. Lane M: H9812.

S1-PFGE indicated that each of the 12 transconjugants carrying blaNDM harbored only one plasmid (Fig. 1). The IncB/O type replicon was detected in 10 transconjugants carrying blaNDM, with the exceptions of IncX3 in WF3-41-T1 and IncHI2/ST3 in WF5-5-T1, and the sizes of the IncB/O plasmids ranged from ∼140 kb to ∼340 kb (Fig. 1 and Table 1). Previous studies have shown that blaNDM is often located in IncFII, IncX3, and IncA/C-type plasmids (25–28). However, in this study, blaNDM was primarily in IncB/O type plasmids, which were found recently to carry blaNDM in Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae from humans in China (29). These data suggested that an IncB/O-type plasmid played a role in the dissemination of blaNDM in China, indicating further surveillance is needed for determining the prevalence of IncB/O plasmids carrying blaNDM. Notably, we identified mcr-1 and blaNDM-4 in an IncHI2/ST3-type plasmid of about 400 kb in transconjugants WF5-5-T1 (Fig. 1 and Table 1). Each of the IncB/O plasmids had different restriction patterns, which even differed between same-sized plasmids (∼140 kb). This indicated that the plasmids carrying blaNDM have undergone a complex evolutionary process resulting in diverse plasmids in the same farm.

To investigate the genetic backgrounds of regions flanking the blaNDM gene, PCR was performed using an established technique with primers ISAba125ext or ISA125A and bleo-Rev (25). A portion of ISAba125 was present upstream of blaNDM in 11 plasmids, while the entire ISAba125 element was found upstream of blaNDM in the IncB/O plasmid in WF3-7-T1. The bleMBL gene was identified downstream of blaNDM in all of the plasmids carrying blaNDM. These results confirmed that ISAba125 plays an important role in the acquisition of blaNDM and bleMBL among the diverse IncB/O plasmids in this study, similar to other blaNDM-type plasmids (25).

In conclusion, our study documents a high incidence of E. coli strains harboring mcr-1 and blaNDM that did not result from clonal dissemination. The dissemination of mcr-1 in these E. coli isolates was mediated by diverse IncI2 plasmids, while diverse IncB/O plasmids were responsible for the dissemination of blaNDM. More striking is the colocalization of mcr-1 and blaNDM-4 in an IncHI2/ST3 plasmid in one E. coli strain, which will inevitably accelerate the horizontal transmission of carbapenem and colistin resistances among Enterobacteriaceae species, including the human pathogens. Our data and those from previous reports stress the urgent need for limiting and monitoring the use of colistin treatments in animals to restrict the further dissemination of blaNDM-mcr-1. To our knowledge, this is the first description of the co-spread of blaNDM and mcr-1 in a single IncHI2/ST3 plasmid in Enterobacteriaceae species.

ACKNOWLEDGMENTS

This study was supported by the Scientific and Technological Projects of Qingdao (grant no. 16-5-1-49-jch), the Priority Academic Talent Team Cultivation Program of Shandong Colleges and Universities, the National Natural Science Foundation of China (grant no. 31502122), the Natural Science Foundation of Shandong Province of China (grant no. BS2015NY005), and the Advanced Talents Foundation of Qingdao Agricultural University (grant no. 663/1115014).

The authors declare no conflicts of interest.

REFERENCES

  • 1.Doi Y, Paterson DL. 2015. Carbapenemase-producing Enterobacteriaceae. Semin Respir Crit Care Med 36:74–84. doi: 10.1055/s-0035-1544208. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.Liu YY, Wang Y, Walsh TR, Yi LX, Zhang R, Spencer J, Doi Y, Tian G, Dong B, Huang X, Yu LF, Gu D, Ren H, Chen X, Lv L, He D, Zhou H, Liang Z, Liu JH, Shen J. 2016. Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological study. Lancet Infect Dis 16:161–168. doi: 10.1016/S1473-3099(15)00424-7. [DOI] [PubMed] [Google Scholar]
  • 3.Arcilla MS, van Hattem JM, Matamoros S, Melles DC, Penders J, de Jong MD, Schultsz C, COMBAT consortium . 2016. Dissemination of the mcr-1 colistin resistance gene. Lancet Infect Dis 16:147–149. doi: 10.1016/S1473-3099(15)00541-1. [DOI] [PubMed] [Google Scholar]
  • 4.Falgenhauer L, Waezsada SE, Yao Y, Imirzalioglu C, Kasbohrer A, Roesler U, Michael GB, Schwarz S, Werner G, Kreienbrock L, Chakraborty T, RESET consortium . 2016. Colistin resistance gene mcr-1 in extended-spectrum beta-lactamase-producing and carbapenemase-producing Gram-negative bacteria in Germany. Lancet Infect Dis 16:282–283. doi: 10.1016/S1473-3099(16)00009-8. [DOI] [PubMed] [Google Scholar]
  • 5.Suzuki S, Ohnishi M, Kawanishi M, Akiba M, Kuroda M. 2016. Investigation of a plasmid genome database for colistin-resistance gene mcr-1. Lancet Infect Dis 16:284–285. doi: 10.1016/S1473-3099(16)00008-6. [DOI] [PubMed] [Google Scholar]
  • 6.Stoesser N, Mathers AJ, Moore CE, Day NP, Crook DW. 2016. Colistin resistance gene mcr-1 and pHNSHP45 plasmid in human isolates of Escherichia coli and Klebsiella pneumoniae. Lancet Infect Dis 16:285–286. doi: 10.1016/S1473-3099(16)00010-4. [DOI] [PubMed] [Google Scholar]
  • 7.Zurfuh K, Poirel L, Nordmann P, Nuesch-Inderbinen M, Hachler H, Stephan R. 2016. Occurrence of the plasmid-borne mcr-1 colistin resistance gene in extended-spectrum-β-lactamase-producing Enterobacteriaceae in river water and imported vegetable samples in Switzerland. Antimicrob Agents Chemother 60:2594–2595. doi: 10.1128/AAC.00066-16. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8.Haenni M, Poirel L, Kieffer N, Chatre P, Saras E, Metayer V, Dumoulin R, Nordmann P, Madec JY. 2016. Co-occurrence of extended spectrum beta lactamase and MCR-1 encoding genes on plasmids. Lancet Infect Dis 16:281–282. doi: 10.1016/S1473-3099(16)00007-4. [DOI] [PubMed] [Google Scholar]
  • 9.Yao X, Doi Y, Zeng L, Lv L, Liu JH. 2016. Carbapenem-resistant and colistin-resistant Escherichia coli co-producing NDM-9 and MCR-1. Lancet Infect Dis 16:288–289. doi: 10.1016/S1473-3099(16)00057-8. [DOI] [PubMed] [Google Scholar]
  • 10.Du H, Chen L, Tang YW, Kreiswirth BN. 2016. Emergence of the mcr-1 colistin resistance gene in carbapenem-resistant Enterobacteriaceae. Lancet Infect Dis 16:287–288. doi: 10.1016/S1473-3099(16)00056-6. [DOI] [PubMed] [Google Scholar]
  • 11.Sun J, Yang RS, Zhang Q, Feng Y, Fang LX, Xia J, Li L, Lv XY, Duan JH, Liao XP, Liu YH. 2016. Co-transfer of blaNDM-5 and mcr-1 by an IncX3-X4 hybrid plasmid in Escherichia coli. Nat Microbiol 1:16176. doi: 10.1038/nmicrobiol.2016.176. [DOI] [PubMed] [Google Scholar]
  • 12.CLSI. 2015. Performance standards for antimicrobial susceptibility testing; 25th informational supplement. CLSI document M100-S25 CLSI, Wayne, PA. [Google Scholar]
  • 13.CLSI. 2015. Performance standards for antimicrobial disk and dilution susceptibility tests for bacteria isolated from animals; approved standard—4th ed. and supplement. VET01A4E and VET01S3E CLSI, Wayne, PA. [Google Scholar]
  • 14.Poirel L, Walsh TR, Cuvillier V, Nordmann P. 2011. Multiplex PCR for detection of acquired carbapenemase genes. Diagn Microbiol Infect Dis 70:119–123. doi: 10.1016/j.diagmicrobio.2010.12.002. [DOI] [PubMed] [Google Scholar]
  • 15.Zong Z, Zhang X. 2013. blaNDM-1-carrying Acinetobacter johnsonii detected in hospital sewage. J Antimicrob Chemother 68:1007–1010. doi: 10.1093/jac/dks505. [DOI] [PubMed] [Google Scholar]
  • 16.Shen Z, Wang Y, Shen Y, Shen J, Wu C. 2016. Early emergence of mcr-1 in Escherichia coli from food-producing animals. Lancet Infect Dis 16:293. doi: 10.1016/S1473-3099(16)00061-X. [DOI] [PubMed] [Google Scholar]
  • 17.Chen D, Gong L, Walsh TR, Lan R, Wang T, Zhang J, Mai W, Ni N, Lu J, Xu J, Li J. 2016. Infection by and dissemination of NDM-5-producing Escherichia coli in China. J Antimicrob Chemother 71:563–565. doi: 10.1093/jac/dkv352. [DOI] [PubMed] [Google Scholar]
  • 18.Chen L, Chen ZL, Liu JH, Zeng ZL, Ma JY, Jiang HX. 2007. Emergence of RmtB methylase-producing Escherichia coli and Enterobacter cloacae isolates from pigs in China. J Antimicrob Chemother 59:880–885. doi: 10.1093/jac/dkm065. [DOI] [PubMed] [Google Scholar]
  • 19.Wang X, Li H, Zhao C, Chen H, Liu J, Wang Z, Wang Q, Zhang Y, He W, Zhang F, Wang H. 2014. Novel NDM-9 metallo-beta-lactamase identified from a ST107 Klebsiella pneumoniae strain isolated in China. Int J Antimicrob Agents 44:90–91. doi: 10.1016/j.ijantimicag.2014.04.010. [DOI] [PubMed] [Google Scholar]
  • 20.Carattoli A, Bertini A, Villa L, Falbo V, Hopkins KL, Threlfall EJ. 2005. Identification of plasmids by PCR-based replicon typing. J Microbiol Methods 63:219–228. doi: 10.1016/j.mimet.2005.03.018. [DOI] [PubMed] [Google Scholar]
  • 21.Johnson TJ, Bielak EM, Fortini D, Hansen LH, Hasman H, Debroy C, Nolan LK, Carattoli A. 2012. Expansion of the IncX plasmid family for improved identification and typing of novel plasmids in drug-resistant Enterobacteriaceae. Plasmid 68:43–50. doi: 10.1016/j.plasmid.2012.03.001. [DOI] [PubMed] [Google Scholar]
  • 22.Chen L, Chavda KD, Al Laham N, Melano RG, Jacobs MR, Bonomo RA, Kreiswirth BN. 2013. Complete nucleotide sequence of a blaKPC-harboring IncI2 plasmid and its dissemination in New Jersey and New York hospitals. Antimicrob Agents Chemother 57:5019–5025. doi: 10.1128/AAC.01397-13. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 23.Garcia-Fernandez A, Carattoli A. 2010. Plasmid double locus sequence typing for IncHI2 plasmids, a subtyping scheme for the characterization of IncHI2 plasmids carrying extended-spectrum beta-lactamase and quinolone resistance genes. J Antimicrob Chemother 65:1155–1161. doi: 10.1093/jac/dkq101. [DOI] [PubMed] [Google Scholar]
  • 24.Hasman H, Hammerum AM, Hansen F, Hendriksen RS, Olesen B, Agerso Y, Zankari E, Leekitcharoenphon P, Stegger M, Kaas RS, Cavaco LM, Hansen DS, Aarestrup FM, Skov RL. 2015. Detection of mcr-1 encoding plasmid-mediated colistin-resistant Escherichia coli isolates from human bloodstream infection and imported chicken meat, Denmark 2015. Euro Surveill 20:pii=30085 http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=21331. [DOI] [PubMed] [Google Scholar]
  • 25.Poirel L, Dortet L, Bernabeu S, Nordmann P. 2011. Genetic features of blaNDM-1-positive Enterobacteriaceae. Antimicrob Agents Chemother 55:5403–5407. doi: 10.1128/AAC.00585-11. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.Rahman M, Shukla SK, Prasad KN, Ovejero CM, Pati BK, Tripathi A, Singh A, Srivastava AK, Gonzalez-Zorn B. 2014. Prevalence and molecular characterisation of New Delhi metallo-beta-lactamases NDM-1, NDM-5, NDM-6 and NDM-7 in multidrug-resistant Enterobacteriaceae from India. Int J Antimicrob Agents 44:30–37. doi: 10.1016/j.ijantimicag.2014.03.003. [DOI] [PubMed] [Google Scholar]
  • 27.Wailan AM, Paterson DL, Kennedy K, Ingram PR, Bursle E, Sidjabat HE. 2015. Genomic characteristics of NDM-producing Enterobacteriaceae isolates in Australia and their blaNDM genetic contexts. Antimicrob Agents Chemother 60:136–141. doi: 10.1128/AAC.01243-15. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 28.Poirel L, Schrenzel J, Cherkaoui A, Bernabeu S, Renzi G, Nordmann P. 2011. Molecular analysis of NDM-1-producing enterobacterial isolates from Geneva, Switzerland. J Antimicrob Chemother 66:1730–1733. doi: 10.1093/jac/dkr174. [DOI] [PubMed] [Google Scholar]
  • 29.An J, Guo L, Zhou L, Ma Y, Luo Y, Tao C, Yang J. 2016. NDM-producing Enterobacteriaceae in a Chinese hospital, 2014–2015: identification of NDM-producing Citrobacter werkmanii and acquisition of blaNDM-1-carrying plasmid in vivo in a clinical Escherichia coli isolate. J Med Microbiol 65:1253–1259. doi: 10.1099/jmm.0.000357. [DOI] [PubMed] [Google Scholar]
  • 30.Wirth T, Falush D, Lan R, Colles F, Mensa P, Wieler LH, Karch H, Reeves PR, Maiden MC, Ochman H, Achtman M. 2006. Sex and virulence in Escherichia coli: an evolutionary perspective. Mol Microbiol 60:1136–1151. doi: 10.1111/j.1365-2958.2006.05172.x. [DOI] [PMC free article] [PubMed] [Google Scholar]

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