Skip directly to search Skip directly to A to Z list Skip directly to page options Skip directly to site content

Volume 24, Number 4—April 2018


mcr-1 in Carbapenemase-Producing Klebsiella pneumoniae with Hospitalized Patients, Portugal, 2016–2017

Ana Constança Mendes1, Ângela Novais1, Joana Campos, Carla Rodrigues, Cláudia Santos, Patrícia Antunes, Helena Ramos, and Luísa PeixeComments to Author 
Author affiliations: Centro Hospitalar do Porto, Porto, Portugal (A.C. Mendes, C. Santos, H. Ramos); Faculdade de Farmácia, Universidade do Porto, Porto (Â. Novais, J. Campos, C. Rodrigues, P. Antunes, L. Peixe); Faculdade de Ciências da Nutrição e Alimentação, Universidade do Porto, Porto (P. Antunes)

Cite This Article


Highlight and copy the desired format.

EID Mendes A, Novais Â, Campos J, Rodrigues C, Santos C, Antunes P, et al. mcr-1 in Carbapenemase-Producing Klebsiella pneumoniae with Hospitalized Patients, Portugal, 2016–2017. Emerg Infect Dis. 2018;24(4):762-766.
AMA Mendes A, Novais Â, Campos J, et al. mcr-1 in Carbapenemase-Producing Klebsiella pneumoniae with Hospitalized Patients, Portugal, 2016–2017. Emerging Infectious Diseases. 2018;24(4):762-766. doi:10.3201/eid2404.171787.
APA Mendes, A., Novais, Â., Campos, J., Rodrigues, C., Santos, C., Antunes, P....Peixe, L. (2018). mcr-1 in Carbapenemase-Producing Klebsiella pneumoniae with Hospitalized Patients, Portugal, 2016–2017. Emerging Infectious Diseases, 24(4), 762-766.


We describe a hospital-based outbreak caused by multidrug-resistant, Klebsiella pneumoniae carbapenemase 3–producing, mcr-1–positive K. pneumoniae sequence type 45 in Portugal. mcr-1 was located in an IncX4 plasmid. Our data highlight the urgent need for systematic surveillance of mcr-1 to support adequate therapeutic choices in the nosocomial setting.

Infections with carbapenemase-producing Enterobacteriaceae (CPE), such as Klebsiella pneumoniae, have been increasing since 2011 in hospitalized patients in several countries in Europe, especially those with high resistance rates (; The emergence of mobilized colistin resistance (MCR) genes is particularly concerning because colistin is being intensively used as a last resource antimicrobial drug for treating CPE infections (1,2). In Europe, sporadic clinical CPE isolates with mcr-1 have been reported (3,4). Because CPE has increased at an alarming pace in Portugal (5,6), we evaluated the occurrence of mcr-1 among CPE isolated from patients admitted to Centro Hospitalar do Porto, a tertiary and university hospital in Porto, Portugal.

The Study

Figure 1

Thumbnail of Selection for and testing of patients with Klebsiella pneumoniae carbapenemase 3–producing mcr-1–positive Enterobacteriaceae, Porto, Portugal, 2016–2017. A) Flowchart demonstrating rationale for sample selection. First, we screened for asymptomatic carriage of CPE in the gastrointestinal tract (i.e., colonization by CPE) by testing patient fecal samples with Brilliance CRE Agar (Oxoid, Basingstoke, UK); Xpert Carba-R (Cepheid, Sunnyvale, CA, USA); and VITEK 2 (bioMérieux, Marcy l’Et

Figure 1. Selection for and testing of patients with Klebsiella pneumoniae carbapenemase 3–producing mcr-1–positive Enterobacteriaceae, Porto, Portugal, 2016–2017. A) Flowchart demonstrating rationale for sample selection. First, we screened for asymptomatic carriage of CPE...

Figure 2

Thumbnail of Alignment of representative mcr-1–harboring IncX4 plasmids from different isolation sources and geographic regions. The mcr-1–harboring plasmid pAN_M1A was used as a reference plasmid. The outermost circle is an annotation of the reference plasmid and shows the direction of transcriptional open-reading frames. The pil loci and other genes (gray), replication-associated genes (dark blue), antimicrobial drug resistance gene (red), and insertion sequence (green) are indicated. The stra

Figure 2. Alignment of representative mcr-1–harboring IncX4 plasmids from different isolation sources and geographic regions. The mcr-1–harboring plasmid pAN_M1A was used as a reference plasmid. The outermost circle is an annotation of the...

Using rectal swab specimens from 5,361 patients admitted to Centro Hospitalar do Porto during October 2015–July 2017, we screened for carbapenemase-positive isolates using Brilliance CRE Agar (Oxoid, Basingstoke, UK), Blue-carba test (7), and real-time PCR for carbapenemase genes (Xpert Carba-R; Cepheid, Sunnyvale, CA, USA) (Figure 1, panel A). We identified 283 patients with 359 CPE-positive samples available for further testing. Of the 359 isolates, 252 (75% K. pneumoniae–positive) were from patient fecal samples and 107 (86% K. pneumoniae-positive) were from other types of patient samples (e.g., blood, urine). We then screened these isolates for mcr-1, blaCTX-M-I-like genes, and blaKPC using PCR and sequencing (5,8,9). We determined the antimicrobial drug susceptibility profiles of the mcr-1–positive isolates by the broth microdilution method for colistin ( and by disk diffusion for the other antimicrobial drugs using Clinical and Laboratory Standards Institute/European Committee on Antimicrobial Susceptibility Testing guidelines ( We evaluated clonal relatedness among K. pneumoniae isolates by multilocus sequence and wzi capsular typing ( = pubmlst_klebsiella_seqdef_public) and assessed plasmid replicon content using PCR (5). We performed whole-genome sequencing with 2 isolates of the predominant K. pneumoniae clones by Hi Seq 2500 Sequencing System (Illumina Inc., San Diego, CA, USA) (2 × 150 bp paired-ended reads, coverage 100×). We assembled reads de novo using SPAdes version 3.9.0 ( and annotated contigs with Prokka ( We used tools from the Center for Genomic Epidemiology ( to assess antimicrobial drug resistance genes and replicons and PLACNETw ( for plasmid reconstruction. We located mcr-1 in the IncX4 plasmid near the replication (pirF) and maintenance (parA) conserved regions by PCR and sequencing (Figure 2).

We identified 24 carbapenemase-producing and MCR-1–producing K. pneumoniae isolates from samples collected during September 2016–February 2017 from 16 hospitalized patients (Figure 1, panel B). Seventeen isolates were colonizers (i.e., bacteria of the patients’ gastrointestinal tract), and 7 were from other parts of the body (3 urine, 2 blood, 2 other biologic fluids) (Table). We recovered 1–4 isolates/patient; 10 colonizing isolates were from intensive care units. Patients (9 men, 7 women) were 50–87 years of age, and their clinical history included prolonged hospitalization (median 47 d, range 12–151 d); complicated conditions; and, for many, surgical interventions, immunosuppression, or previous antimicrobial drug use (usually β-lactams) favoring infection or colonization by multidrug-resistant (MDR) mcr-1–positive strains (10). Fecal samples were negative for CPE at admission (14/16 patients screened) and for a median of 15 (range 3–94) days after admission (Figure 1, panel B). Five patients had 1 or 2 extraintestinal infections with an MCR-1–producing isolate, sometimes with an isolate identical to one previously detected in their gastrointestinal tract.

Colistin use and travel abroad were not recorded for any patient before mcr-1 detection; however, 5 of the 16 patients had been hospitalized in the previous 6 months. Patients were treated for CPE infection with colistin and a carbapenem, which was supplemented with fosfomycin, tigecycline, or piperacillin/tazobactam depending on clinical criteria. We missed colistin resistance initially because we used conventional antimicrobial susceptibility tests VITEK 2 (bioMérieux, Marcy l’Etoile, France) and Etest (bioMérieux), which are unreliable at detecting colistin resistance. Adequate colistin resistance monitoring ( and mcr-1 screening for CPE isolates was implemented in July 2017.

Isolates carrying mcr-1.1 were resistant to colistin (MIC 4–8 mg/L), produced K. pneumoniae carbapenemase 3 (KPC-3), and most (79%) produced CTX-M-15 β-lactamase. Besides 100% resistance to third and fourth generation cephalosporins and monobactams, K. pneumoniae isolates were also frequently resistant to nalidixic acid (100%), ciprofloxacin (96%), tigecycline (96%), tetracycline (92%), tobramycin (88%), gentamicin (88%), fosfomycin (83%), trimethoprim/sulfamethoxazole (79%), and chloramphenicol (67%) (Table). All isolates were susceptible to amikacin (which was contraindicated for some patients because of renal insufficiency) and ceftazidime/avibactam (which was not available).

All but 1 K. pneumoniae isolate belonged to sequence type (ST) 45 and carried wzi101/K24, a clone that has been infrequently detected among clinical MDR K. pneumoniae isolates in Portugal (5,6) but has circulated among KPC-3 producers (without mcr-1) during the same period (L. Peixe, unpub. data). We detected 1 mcr-1–positive K. pneumoniae (capsular type KL122) ST1112 isolate from the pus of an abdominal wall abscess in a patient having mcr-1–positive ST45 in previously collected fecal and urine samples (Table). The 2 whole-genome–sequenced K. pneumoniae ST45 isolates had genes encoding resistance to aminoglycosides [aac(6’)Ib-cr,aac(3)-IIa]; β-lactams (blaKPC-3, blaSHV-1, blaOXA-1), fluoroquinolones [qnrB66, aac(6’)Ib-cr,oqxAB], and other antimicrobial drugs [catB4,tet(A)]; 1 of the 2 isolates possessed additional genes aph(4)-Ib, strAB, blaTEM-1B, blaCTX-M-15, catA1, sul2, and dfrA14.

In all mcr-1–positive isolates, the gene was located in an IncX4-type plasmid (Figure 2). Comparative genomics revealed that this plasmid (pAN_M1A) is circulating among diverse hosts (humans, pig, poultry) and the environment in many different countries, including Portugal (11). We identified blaKPC-3 in a Tn4401d isoform in an ≈58-kb IncN-ST15 plasmid, a minority platform in our previous survey (5); blaCTX-M-15 was associated with multireplicon plasmid IncFIIK-FIA-FIB. We deposited this whole-genome shotgun project at DDBJ/European Nucleotide Archive/GenBank under accession no. PEHI00000000.

We found that 5.7% (16/283) of hospitalized patients had gastrointestinal tracts colonized with mcr-1–positive CPE, and in 1.8% (5/283) of these patients, an infection developed; these rates are comparable with those reported in China (up to 6.2% for fecal colonization, 1% for infections) (10,12). In China, only 1 outbreak involving mcr-1–carrying clinical isolates has been reported (13), and in Europe, a low occurrence (<1%) and sporadic clinical cases have been reported (3,4). Colistin is a critical last resource antimicrobial drug; prolonged carriage of mcr-1–positive MDR strains (especially by patients at discharge) represents a risk for subsequent infections and dissemination to other Enterobacteriaceae species. Of note, identifying CPE asymptomatic carriers at discharge is a practice recommended in Portugal, though not mandatory.

Considering the absence of CPE at admission, nosocomial acquisition and in-hospital dissemination of KPC-3–producing strains carrying mcr-1 is plausible; however, we cannot rule out that other K. pneumoniae lineages or Escherichia coli might have been the source of mcr-1. Although the prevalence of colonization of humans by mcr-1–positive strains is unknown in Portugal, previous detection of mcr-1 in livestock, such as K. pneumoniae ST45 in pigs, suggests transmission through the food chain and wider dispersion of MCR-1–producing Enterobacteriaceae (8,11,14,15).


We report the emergence of mcr-1 in MDR KPC-3–producing K. pneumoniae associated with an unnoticed outbreak. High rates of CPE and colistin use (2,5,6) together with an ongoing community-based dissemination of mcr forebodes future similar events. Our data stress the need for a concerted action involving different professionals and healthcare institutions to monitor and contain the spread of mcr across human and veterinary niches, the food chain, and the environment.

Ms. Mendes is a biomedical scientist in the Microbiology Service and Molecular Biology Unit at Centro Hospitalar do Porto (Porto, Portugal). She is currently pursuing her doctorate, with research interests in molecular epidemiology of multidrug-resistant Enterobacteriaceae.



This work received financial support from the European Union (FEDER funds POCI/01/0145/FEDER/007728) and National Funds (Fundação para a Ciência e Tecnologia and Ministério da Educação e Ciência) under the partnership agreement PT2020 UID/MULTI/04378/2013. Fellowship support was provided by Fundação para a Ciência e Tecnologia through Programa Operacional Capital Humano to Â.N. (grant no. SFRH/BPD/104927/2014), to J.C. (grant no. SFRH/BD/93091/2013), and to C.R. (grant no. SFRH/BD/84341/2012).



  1. Liu YY, Wang Y, Walsh TR, Yi LX, Zhang R, Spencer J, et al. 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. 2016;16:1618. DOIPubMed
  2. European Centre for Disease Prevention and Control; European Food Safety Authority; European Medicines Agency. ECDC/EFSA/EMA second joint report on the integrated analysis of the consumption of antimicrobial agents and occurrence of antimicrobial resistance in bacteria from humans and food-producing animals—Joint Interagency Antimicrobial Consumption and Resistance Analysis (JIACRA) Report. EFSA Journal. 2017;15:4872.
  3. Huang TD, Bogaerts P, Berhin C, Hoebeke M, Bauraing C, Glupczynski Y; a multicentre study group. Increasing proportion of carbapenemase-producing Enterobacteriaceae and emergence of a MCR-1 producer through a multicentric study among hospital-based and private laboratories in Belgium from September to November 2015. Euro Surveill. 2017;22:30530. DOIPubMed
  4. Di Pilato V, Arena F, Tascini C, Cannatelli A, Henrici De Angelis L, Fortunato S, et al. mcr-1.2, a new mcr variant carried on a transferable plasmid from a colistin-resistant KPC carbapenemase-producing Klebsiella pneumoniae strain of sequence type 512. Antimicrob Agents Chemother. 2016;60:56125. DOIPubMed
  5. Rodrigues C, Bavlovič J, Machado E, Amorim J, Peixe L, Novais Â. KPC-3-producing Klebsiella pneumoniae in Portugal linked to previously circulating non-CG258 lineages and uncommon genetic platforms (Tn4401d-IncFIA and Tn4401d-IncN). Front Microbiol. 2016;7:1000. DOIPubMed
  6. Manageiro V, Ferreira E, Almeida J, Barbosa S, Simões C, Bonomo RA, et al.; Antibiotic Resistance Surveillance Program in Portugal (ARSIP). Predominance of KPC-3 in a survey for carbapenemase-producing Enterobacteriaceae in Portugal. Antimicrob Agents Chemother. 2015;59:358892. DOIPubMed
  7. Pires J, Novais A, Peixe L. Blue-carba, an easy biochemical test for detection of diverse carbapenemase producers directly from bacterial cultures. J Clin Microbiol. 2013;51:42813. DOIPubMed
  8. Campos J, Cristino L, Peixe L, Antunes P. MCR-1 in multidrug-resistant and copper-tolerant clinically relevant Salmonella 1,4,[5],12:i:- and S. Rissen clones in Portugal, 2011 to 2015. Euro Surveill. 2016;21:30270. DOIPubMed
  9. Falgenhauer L, Waezsada S-E, Yao Y, Imirzalioglu C, Käsbohrer A, Roesler U, et al.; RESET consortium. Colistin resistance gene mcr-1 in extended-spectrum β-lactamase-producing and carbapenemase-producing Gram-negative bacteria in Germany. Lancet Infect Dis. 2016;16:2823. DOIPubMed
  10. Wang Y, Tian GB, Zhang R, Shen Y, Tyrrell JM, Huang X, et al. Prevalence, risk factors, outcomes, and molecular epidemiology of mcr-1-positive Enterobacteriaceae in patients and healthy adults from China: an epidemiological and clinical study. Lancet Infect Dis. 2017;17:3909. DOIPubMed
  11. Tacão M, Tavares RDS, Teixeira P, Roxo I, Ramalheira E, Ferreira S, et al. mcr-1 and blaKPC-3 in Escherichia coli sequence type 744 after meropenem and colistin therapy, Portugal. Emerg Infect Dis. 2017;23:141921. DOIPubMed
  12. Zhong LL, Phan HTT, Shen C, Doris-Vihta K, Sheppard AE, Huang X, et al. High rates of human fecal carriage of mcr-1–positive multidrug-resistant Enterobacteriaceae emerge in China in association with successful plasmid families. Clin Infect Dis. 2017.DOIPubMed
  13. Tian GB, Doi Y, Shen J, Walsh TR, Wang Y, Zhang R, et al. MCR-1-producing Klebsiella pneumoniae outbreak in China. Lancet Infect Dis. 2017;17:577. DOIPubMed
  14. Kieffer N, Aires-de-Sousa M, Nordmann P, Poirel L. High rate of MCR-1–producing Escherichia coli and Klebsiella pneumoniae among pigs, Portugal. Emerg Infect Dis. 2017;23:20239. DOIPubMed
  15. Manageiro V, Clemente L, Graça R, Correia I, Albuquerque T, Ferreira E, et al. New insights into resistance to colistin and third-generation cephalosporins of Escherichia coli in poultry, Portugal: Novel blaCTX-M-166and blaESACgenes. Int J Food Microbiol. 2017;263:6773. DOIPubMed





Cite This Article

DOI: 10.3201/eid2404.171787

1These authors contributed equally to this article.

Table of Contents – Volume 24, Number 4—April 2018


Please use the form below to submit correspondence to the authors or contact them at the following address:

Luísa Peixe, UCIBIO, Laboratório de Microbiologia, Faculdade de Farmácia, Universidade do Porto, Rua Jorge de Viterbo Ferreira, n. 228, 4050-313 Porto, Portugal

character(s) remaining.

Comment submitted successfully, thank you for your feedback.