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Novel Aspects of the SubA Subunit of the Subtilase Cytotoxin. Toxins (Basel) 2022; 14:toxins14020156. [PMID: 35202183 PMCID: PMC8876466 DOI: 10.3390/toxins14020156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 02/17/2022] [Accepted: 02/18/2022] [Indexed: 02/04/2023] Open
Abstract
The subtilase cytotoxin (SubAB) belongs to the family of AB5 toxins and is produced together with Shiga toxin (Stx) by certain Stx-producing E. coli strains (STEC). For most AB-type toxins, it is assumed that cytotoxic effects can only be induced by a complete holotoxin complex consisting of SubA and SubB. However, it has been shown for SubAB that the enzymatically active subunit SubA, without its transport and binding domain SubB, induces cell death in different eukaryotic cell lines. Interestingly, the molecular structure of SubA resembles that of the SubAB complex. SubA alone is capable of binding to cells and then being taken up autonomously. Once inside the host cell, SubA is transported, similar to the SubAB holotoxin, via a retrograde transport into the endoplasmatic reticulum (ER). In the ER, it exhibits its enzymatic activity by cleaving the chaperone BiP/GRP78 and thereby triggering cell death. Therefore, the existence of toxic single SubA subunits that have not found a B-pentamer for holotoxin assembly might improve the pathogenic potential of subtilase-producing strains. Moreover, from a pharmacological aspect, SubA might be an interesting molecule for the targeted transport of therapeutic molecules into the ER, in order to investigate and specifically modulate processes in the context of ER stress-associated diseases. Since recent studies on bacterial AB5 toxins contributed mainly to the understanding of the biology of AB-type holotoxins, this mini-review specifically focus on that recently observed single A-effect of the subtilase cytotoxin and addresses whether a fundamental shift of the traditional AB5 paradigm might be required.
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Álvarez RS, Gómez FD, Zotta E, Paton AW, Paton JC, Ibarra C, Sacerdoti F, Amaral MM. Combined Action of Shiga Toxin Type 2 and Subtilase Cytotoxin in the Pathogenesis of Hemolytic Uremic Syndrome. Toxins (Basel) 2021; 13:536. [PMID: 34437406 PMCID: PMC8402323 DOI: 10.3390/toxins13080536] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 07/22/2021] [Accepted: 07/23/2021] [Indexed: 11/17/2022] Open
Abstract
Shiga toxin-producing E. coli (STEC) produces Stx1 and/or Stx2, and Subtilase cytotoxin (SubAB). Since these toxins may be present simultaneously during STEC infections, the purpose of this work was to study the co-action of Stx2 and SubAB. Stx2 + SubAB was assayed in vitro on monocultures and cocultures of human glomerular endothelial cells (HGEC) with a human proximal tubular epithelial cell line (HK-2) and in vivo in mice after weaning. The effects in vitro of both toxins, co-incubated and individually, were similar, showing that Stx2 and SubAB contribute similarly to renal cell damage. However, in vivo, co-injection of toxins lethal doses reduced the survival time of mice by 24 h and mice also suffered a strong decrease in the body weight associated with a lowered food intake. Co-injected mice also exhibited more severe histological renal alterations and a worsening in renal function that was not as evident in mice treated with each toxin separately. Furthermore, co-treatment induced numerous erythrocyte morphological alterations and an increase of free hemoglobin. This work shows, for the first time, the in vivo effects of Stx2 and SubAB acting together and provides valuable information about their contribution to the damage caused in STEC infections.
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Affiliation(s)
- Romina S. Álvarez
- Laboratorio de Fisiopatogenia, Departamento de Fisiología, Instituto de Fisiología y Biofísica Bernardo Houssay (IFIBIO Houssay-CONICET), Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires 1121, Argentina; (R.S.Á.); (F.D.G.); (E.Z.); (C.I.); (F.S.)
| | - Fernando D. Gómez
- Laboratorio de Fisiopatogenia, Departamento de Fisiología, Instituto de Fisiología y Biofísica Bernardo Houssay (IFIBIO Houssay-CONICET), Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires 1121, Argentina; (R.S.Á.); (F.D.G.); (E.Z.); (C.I.); (F.S.)
| | - Elsa Zotta
- Laboratorio de Fisiopatogenia, Departamento de Fisiología, Instituto de Fisiología y Biofísica Bernardo Houssay (IFIBIO Houssay-CONICET), Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires 1121, Argentina; (R.S.Á.); (F.D.G.); (E.Z.); (C.I.); (F.S.)
- Cátedra de Fisiopatología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires 1113, Argentina
| | - Adrienne W. Paton
- Research Centre for Infectious Diseases, Department of Molecular and Biomedical Science, University of Adelaide, Adelaide 5005, Australia; (A.W.P.); (J.C.P.)
| | - James C. Paton
- Research Centre for Infectious Diseases, Department of Molecular and Biomedical Science, University of Adelaide, Adelaide 5005, Australia; (A.W.P.); (J.C.P.)
| | - Cristina Ibarra
- Laboratorio de Fisiopatogenia, Departamento de Fisiología, Instituto de Fisiología y Biofísica Bernardo Houssay (IFIBIO Houssay-CONICET), Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires 1121, Argentina; (R.S.Á.); (F.D.G.); (E.Z.); (C.I.); (F.S.)
| | - Flavia Sacerdoti
- Laboratorio de Fisiopatogenia, Departamento de Fisiología, Instituto de Fisiología y Biofísica Bernardo Houssay (IFIBIO Houssay-CONICET), Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires 1121, Argentina; (R.S.Á.); (F.D.G.); (E.Z.); (C.I.); (F.S.)
| | - María M. Amaral
- Laboratorio de Fisiopatogenia, Departamento de Fisiología, Instituto de Fisiología y Biofísica Bernardo Houssay (IFIBIO Houssay-CONICET), Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires 1121, Argentina; (R.S.Á.); (F.D.G.); (E.Z.); (C.I.); (F.S.)
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Heinisch L, Krause M, Roth A, Barth H, Schmidt H. Cytotoxic Effects of Recombinant StxA2-His in the Absence of Its Corresponding B-Subunit. Toxins (Basel) 2021; 13:toxins13050307. [PMID: 33925951 PMCID: PMC8145687 DOI: 10.3390/toxins13050307] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/22/2021] [Accepted: 04/23/2021] [Indexed: 11/16/2022] Open
Abstract
AB5 protein toxins are produced by certain bacterial pathogens and are composed of an enzymatically active A-subunit and a B-subunit pentamer, the latter being responsible for cell receptor recognition, cellular uptake, and transport of the A-subunit into the cytosol of eukaryotic target cells. Two members of the AB5 toxin family were described in Shiga toxin-producing Escherichia coli (STEC), namely Shiga toxin (Stx) and subtilase cytotoxin (SubAB). The functional paradigm of AB toxins includes the B-subunit being mandatory for the uptake of the toxin into its target cells. Recent studies have shown that this paradigm cannot be maintained for SubAB, since SubA alone was demonstrated to intoxicate human epithelial cells in vitro. In the current study, we raised the hypothesis that this may also be true for the A-subunit of the most clinically relevant Stx-variant, Stx2a. After separate expression and purification, the recombinant Stx2a subunits StxA2a-His and StxB2a-His were applied either alone or in combination in a 1:5 molar ratio to Vero B4, HeLa, and HCT-116 cells. For all cell lines, a cytotoxic effect of StxA2a-His alone was detected. Competition experiments with Stx and SubAB subunits in combination revealed that the intoxication of StxA2a-His was reduced by addition of SubB1-His. This study showed that the enzymatic subunit StxA2a alone was active on different cells and might therefore play a yet unknown role in STEC disease development.
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Affiliation(s)
- Laura Heinisch
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (L.H.); (M.K.); (A.R.)
| | - Maike Krause
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (L.H.); (M.K.); (A.R.)
| | - Astrid Roth
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (L.H.); (M.K.); (A.R.)
| | - Holger Barth
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany;
| | - Herbert Schmidt
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (L.H.); (M.K.); (A.R.)
- Correspondence: ; Tel.: +49-711-459-22305
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Tsutsuki H, Ogura K, Moss J, Yahiro K. Host response to the subtilase cytotoxin produced by locus of enterocyte effacement-negative Shiga-toxigenic Escherichia coli. Microbiol Immunol 2020; 64:657-665. [PMID: 32902863 DOI: 10.1111/1348-0421.12841] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 08/05/2020] [Accepted: 09/07/2020] [Indexed: 12/26/2022]
Abstract
Shiga-toxigenic Escherichia coli (STEC) is a major bacterium responsible for disease resulting from foodborne infection, including bloody diarrhea and hemolytic uremic syndrome. STEC produces important virulence factors such as Shiga toxin (Stx) 1 and/or 2. In the STEC family, some locus of enterocyte effacement-negative STEC produce two different types of cytotoxins, namely, Stx2 and subtilase cytotoxin (SubAB). The Stx2 and SubAB cytotoxins are structurally similar and composed of one A subunit and pentamer of B subunits. The catalytically active A subunit of SubAB is a subtilase-like serine protease and specifically cleaves an endoplasmic reticulum (ER) chaperone 78-kDa glucose-regulated protein (GRP78/BiP), a monomeric ATPase that is crucial in protein folding and quality control. The B subunit binds to cell surface receptors. SubAB recognizes sialic carbohydrate-modified cell surface proteins as a receptor. After translocation into cells, SubAB is delivered to the ER, where it cleaves GRP78/BiP. SubAB-catalyzed BiP cleavage induces ER stress, which causes various cell events including inhibition of protein synthesis, suppression of nuclear factor-kappa B activation, apoptotic cell death, and stress granules formation. In this review, we describe SubAB, the SubAB receptor, and the mechanism of cell response to the toxin.
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Affiliation(s)
- Hiroyasu Tsutsuki
- Department of Microbiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan
| | - Kohei Ogura
- Advanced Health Care Science Research Unit, Institute for Frontier Science Initiative, Kanazawa University, Kanazawa, Japan
| | - Joel Moss
- Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Kinnosuke Yahiro
- Department of Molecular Infectiology, Graduate School of Medicine, Chiba University, Chiba, Japan
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Wyrsch ER, Chowdhury PR, Jarocki VM, Brandis KJ, Djordjevic SP. Duplication and diversification of a unique chromosomal virulence island hosting the subtilase cytotoxin in Escherichia coli ST58. Microb Genom 2020; 6:e000387. [PMID: 32519937 PMCID: PMC7371111 DOI: 10.1099/mgen.0.000387] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 05/18/2020] [Indexed: 12/17/2022] Open
Abstract
The AB5 cytotoxins are important virulence factors in Escherichia coli. The most notable members of the AB5 toxin families include Shiga toxin families 1 (Stx1) and 2 (Stx2), which are associated with enterohaemorrhagic E. coli infections causing haemolytic uraemic syndrome and haemorrhagic colitis. The subAB toxins are the newest and least well understood members of the AB5 toxin gene family. The subtilase toxin genes are divided into a plasmid-based variant, subAB1, originally described in enterohaemorrhagic E. coli O113:H21, and distinct chromosomal variants, subAB2, that reside in pathogenicity islands encoding additional virulence effectors. Previously we identified a chromosomal subAB2 operon within an E. coli ST58 strain IBS28 (ONT:H25) taken from a wild ibis nest at an inland wetland in New South Wales, Australia. Here we show the subAB2 toxin operon comprised part of a 140 kb tRNA-Phe chromosomal island that co-hosted tia, encoding an outer-membrane protein that confers an adherence and invasion phenotype and additional virulence and accessory genetic content that potentially originated from known virulence island SE-PAI. This island shared a common evolutionary history with a secondary 90 kb tRNA-Phe pathogenicity island that was presumably generated via a duplication event. IBS28 is closely related [200 single-nucleotide polymorphisms (SNPs)] to four North American ST58 strains. The close relationship between North American isolates of ST58 and IBS28 was further supported by the identification of the only copy of a unique variant of IS26 within the O-antigen gene cluster. Strain ISB28 may be a historically important E. coli ST58 genome sequence hosting a progenitor pathogenicity island encoding subAB.
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Affiliation(s)
- Ethan R. Wyrsch
- ithree institute, University of Technology Sydney, Ultimo, NSW 2007, Australia
- The Australian Centre for Genomic Epidemiological Microbiology, University of Technology Sydney, Ultimo, NSW 2007, Australia
| | - Piklu Roy Chowdhury
- ithree institute, University of Technology Sydney, Ultimo, NSW 2007, Australia
- The Australian Centre for Genomic Epidemiological Microbiology, University of Technology Sydney, Ultimo, NSW 2007, Australia
| | - Veronica M. Jarocki
- ithree institute, University of Technology Sydney, Ultimo, NSW 2007, Australia
- The Australian Centre for Genomic Epidemiological Microbiology, University of Technology Sydney, Ultimo, NSW 2007, Australia
| | - Kate J. Brandis
- Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, Kensington 2052 NSW, Australia
| | - Steven P. Djordjevic
- ithree institute, University of Technology Sydney, Ultimo, NSW 2007, Australia
- The Australian Centre for Genomic Epidemiological Microbiology, University of Technology Sydney, Ultimo, NSW 2007, Australia
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Krause M, Sessler K, Kaziales A, Grahl R, Noettger S, Barth H, Schmidt H. Variants of Escherichia coli Subtilase Cytotoxin Subunits Show Differences in Complex Formation In Vitro. Toxins (Basel) 2019; 11:toxins11120703. [PMID: 31816894 PMCID: PMC6950094 DOI: 10.3390/toxins11120703] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 11/19/2019] [Accepted: 11/27/2019] [Indexed: 12/11/2022] Open
Abstract
The subtilase cytotoxin (SubAB) of Shiga toxin-producing Escherichia coli (STEC) is a member of the AB5 toxin family. In the current study, we analyzed the formation of active homo- and hetero-complexes of SubAB variants in vitro to characterize the mode of assembly of the subunits. Recombinant SubA1-His, SubB1-His, SubA2-2-His, and SubB2-2-His subunits, and His-tag-free SubA2-2 were separately expressed, purified, and biochemically characterized by circular dichroism (CD) spectroscopy, size-exclusion chromatography (SEC), and analytical ultracentrifugation (aUC). To confirm their biological activity, cytotoxicity assays were performed with HeLa cells. The formation of AB5 complexes was investigated with aUC and isothermal titration calorimetry (ITC). Binding of SubAB2-2-His to HeLa cells was characterized with flow cytometry (FACS). Cytotoxicity experiments revealed that the analyzed recombinant subtilase subunits were biochemically functional and capable of intoxicating HeLa cells. Inhibition of cytotoxicity by Brefeldin A demonstrated that the cleavage is specific. All His-tagged subunits, as well as the non-tagged SubA2-2 subunit, showed the expected secondary structural compositions and oligomerization. Whereas SubAB1-His complexes could be reconstituted in solution, and revealed a Kd value of 3.9 ± 0.8 μmol/L in the lower micromolar range, only transient interactions were observed for the subunits of SubAB2-2-His in solution, which did not result in any binding constant when analyzed with ITC. Additional studies on the binding characteristics of SubAB2-2-His on HeLa cells revealed that the formation of transient complexes improved binding to the target cells. Conclusively, we hypothesize that SubAB variants exhibit different characteristics in their binding behavior to their target cells.
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Affiliation(s)
- Maike Krause
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (M.K.); (R.G.)
| | - Katharina Sessler
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany; (K.S.); (S.N.); (H.B.)
| | - Anna Kaziales
- Center for Integrated Protein Science Munich, Department of Chemistry, Technical University of Munich, Lichtenbergstr. 4, 85748 Garching, Germany;
| | - Richard Grahl
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (M.K.); (R.G.)
| | - Sabrina Noettger
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany; (K.S.); (S.N.); (H.B.)
| | - Holger Barth
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany; (K.S.); (S.N.); (H.B.)
| | - Herbert Schmidt
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (M.K.); (R.G.)
- Correspondence: ; Tel.: +49-711-459-22305
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Fierz L, Cernela N, Hauser E, Nüesch-Inderbinen M, Stephan R. Characteristics of Shigatoxin-Producing Escherichia coli Strains Isolated during 2010-2014 from Human Infections in Switzerland. Front Microbiol 2017; 8:1471. [PMID: 28824596 PMCID: PMC5540938 DOI: 10.3389/fmicb.2017.01471] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 07/20/2017] [Indexed: 11/16/2022] Open
Abstract
Objectives: The aim of this study was to characterize a collection of 95 Shigatoxin-producing E.coli (STEC) isolated from human patients in Switzerland during 2010-2014. Methods: We performed O and H serotyping and molecular subtyping. Results: The five most common serogroups were O157, O145, O26, O103, and O146. Of the 95 strains, 35 (36.8%) carried stx1 genes only, 43 strains (45.2%) carried stx2 and 17 (17.9%) harbored combinations of stx1 and stx2 genes. Stx1a (42 strains) and stx2a (32 strains) were the most frequently detected stx subtypes. Genes for intimin (eae), hemolysin (hly), iron-regulated adhesion (iha), and the subtilase cytotoxin subtypes subAB1, subAB2-1, subAB2-2, or subAB2-3 were detected in 70.5, 83.2, 74.7, and 20% of the strains, respectively. Multilocus sequence typing assigned the majority (58.9%) of the isolates to five different clonal complexes (CC), 11, 32, 29, 20, and 165, respectively. CC11 included all O157:[H7] and O55:[H7] isolates. CC32 comprised O145:[H28] isolates, and O145:[H25] belonged to sequence type (ST) 342. CC29 contained isolates of the O26:[H11], O111:[H8] and O118:[Hnt] serogroups, and CC20 encompassed isolates of O51:H49/[Hnt] and O103:[H2]. CC165 included isolates typed O80:[H2]-ST301, all harboring stx2d, eae-ξ, hly, and 66.7% additionally harboring iha. All O80:[H2]-ST301 strains harbored at least 7 genes carried by pS88, a plasmid associated with extraintestinal virulence. Compared to data from Switzerland from the years 2000-2009, an increase of the proportion of non-O157 STEC infections was observed as well as an increase of infections due to STEC O146. By contrast, the prevalence of the highly virulent German clone STEC O26:[H11]-ST29 decreased from 11.3% during 2000-2009 to 1.1% for the time span 2010-2014. The detection of O80:[H2]-ST301 harboring stx2d, eae-ξ, hly, iha, and pS88 related genes suggests an ongoing emergence in Switzerland of an unusual, highly pathogenic STEC serotype. Conclusions: Serotyping and molecular subtyping of clinical STEC demonstrate that although STEC O157 predominates among STEC isolated from diseased humans, non-O157 STEC infections are increasing in Switzerland, including those due to STEC O146:[H2/H21/H28]-ST442/ST738 harboring subAB variants, and the recently emerged STEC O80:[H2]-ST301 harboring eae-ξ and pS88 associated extraintestinal pathogenic virulence genes.
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Affiliation(s)
- Lisa Fierz
- Institute for Food Safety and Hygiene, Swiss National Centre for Enteropathogenic Bacteria and Listeria, Vetsuisse Faculty, University of ZurichZurich, Switzerland
| | - Nicole Cernela
- Institute for Food Safety and Hygiene, Swiss National Centre for Enteropathogenic Bacteria and Listeria, Vetsuisse Faculty, University of ZurichZurich, Switzerland
| | - Elisabeth Hauser
- National Reference Laboratory for Escherichia coli, Department of Biology Safety, Federal Institute for Risk AssessmentBerlin, Germany
| | - Magdalena Nüesch-Inderbinen
- Institute for Food Safety and Hygiene, Swiss National Centre for Enteropathogenic Bacteria and Listeria, Vetsuisse Faculty, University of ZurichZurich, Switzerland
| | - Roger Stephan
- Institute for Food Safety and Hygiene, Swiss National Centre for Enteropathogenic Bacteria and Listeria, Vetsuisse Faculty, University of ZurichZurich, Switzerland
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