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Identification, Shiga toxin subtypes and prevalence of minor serogroups of Shiga toxin-producing Escherichia coli in feedlot cattle feces. Sci Rep 2021; 11:8601. [PMID: 33883564 PMCID: PMC8060326 DOI: 10.1038/s41598-021-87544-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 03/23/2021] [Indexed: 01/12/2023] Open
Abstract
Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens that cause illnesses in humans ranging from mild to hemorrhagic enteritis with complications of hemolytic uremic syndrome and even death. Cattle are a major reservoir of STEC, which reside in the hindgut and are shed in the feces, a major source of food and water contaminations. Seven serogroups, O26, O45, O103, O111, O121, O145 and O157, called ‘top-7’, are responsible for the majority of human STEC infections in North America. Additionally, 151 serogroups of E. coli are known to carry Shiga toxin genes (stx). Not much is known about fecal shedding and prevalence and virulence potential of STEC other than the top-7. Our primary objectives were to identify serogroups of STEC strains, other than the top-7, isolated from cattle feces and subtype stx genes to assess their virulence potential. Additional objective was to develop and validate a novel multiplex PCR assay to detect and determine prevalence of six serogroups, O2, O74, O109, O131, O168, and O171, in cattle feces. A total of 351 strains, positive for stx gene and negative for the top-7 serogroups, isolated from feedlot cattle feces were used in the study. Of the 351 strains, 291 belonged to 16 serogroups and 60 could not be serogrouped. Among the 351 strains, 63 (17.9%) carried stx1 gene and 300 (82.1%) carried stx2, including 12 strains positive for both. The majority of the stx1 and stx2 were of stx1a (47/63; 74.6%) and stx2a subtypes (234/300; 78%), respectively, which are often associated with human infections. A novel multiplex PCR assay developed and validated to detect six serogroups, O2, O74, O109, O131, O168, and O171, which accounted for 86.9% of the STEC strains identified, was utilized to determine their prevalence in fecal samples (n = 576) collected from a commercial feedlot. Four serogroups, O2, O109, O168, and O171 were identified as the dominant serogroups prevalent in cattle feces. In conclusion, cattle shed in the feces a number of STEC serogroups, other than the top-7, and the majority of the strains isolated possessed stx2, particularly of the subtype 2a, suggesting their potential risk to cause human infections.
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2
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Ludwig JB, Shi X, Shridhar PB, Roberts EL, DebRoy C, Phebus RK, Bai J, Nagaraja TG. Multiplex PCR Assays for the Detection of One Hundred and Thirty Seven Serogroups of Shiga Toxin-Producing Escherichia coli Associated With Cattle. Front Cell Infect Microbiol 2020; 10:378. [PMID: 32850480 PMCID: PMC7403468 DOI: 10.3389/fcimb.2020.00378] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 06/18/2020] [Indexed: 12/16/2022] Open
Abstract
Escherichia coli carrying prophage with genes that encode for Shiga toxins are categorized as Shiga toxin-producing E. coli (STEC) pathotype. Illnesses caused by STEC in humans, which are often foodborne, range from mild to bloody diarrhea with life-threatening complications of renal failure and hemolytic uremic syndrome and even death, particularly in children. As many as 158 of the total 187 serogroups of E. coli are known to carry Shiga toxin genes, which makes STEC a major pathotype of E. coli. Seven STEC serogroups, called top-7, which include O26, O45, O103, O111, O121, O145, and O157, are responsible for the majority of the STEC-associated human illnesses. The STEC serogroups, other than the top-7, called “non-top-7” have also been associated with human illnesses, more often as sporadic infections. Ruminants, particularly cattle, are principal reservoirs of STEC and harbor the organisms in the hindgut and shed in the feces, which serves as a major source of food and water contaminations. A number of studies have reported on the fecal prevalence of top-7 STEC in cattle feces. However, there is paucity of data on the prevalence of non-top-7 STEC serogroups in cattle feces, generally because of lack of validated detection methods. The objective of our study was to develop and validate 14 sets of multiplex PCR (mPCR) assays targeting serogroup-specific genes to detect 137 non-top-7 STEC serogroups previously reported to be present in cattle feces. Each assay included 7–12 serogroups and primers were designed to amplify the target genes with distinct amplicon sizes for each serogroup that can be readily identified within each assay. The assays were validated with 460 strains of known serogroups. The multiplex PCR assays designed in our study can be readily adapted by most laboratories for rapid identification of strains belonging to the non-top-7 STEC serogroups associated with cattle.
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Affiliation(s)
- Justin B Ludwig
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, KS, United States
| | - Xiaorong Shi
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, KS, United States
| | - Pragathi B Shridhar
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, KS, United States
| | - Elisabeth L Roberts
- E. coli Reference Center, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA, United States
| | - Chitrita DebRoy
- E. coli Reference Center, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA, United States
| | - Randy K Phebus
- Department of Animal Sciences and Industry/Food Science Institute, Kansas State University, Manhattan, KS, United States
| | - Jianfa Bai
- Veterinary Diagnostic Laboratory, Industry/Food Science Institute, Kansas State University, Manhattan, KS, United States
| | - T G Nagaraja
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, KS, United States
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Collis RM, Biggs PJ, Midwinter AC, Browne AS, Wilkinson DA, Irshad H, French NP, Brightwell G, Cookson AL. Genomic epidemiology and carbon metabolism of Escherichia coli serogroup O145 reflect contrasting phylogenies. PLoS One 2020; 15:e0235066. [PMID: 32584859 PMCID: PMC7316241 DOI: 10.1371/journal.pone.0235066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 06/08/2020] [Indexed: 11/18/2022] Open
Abstract
Shiga toxin-producing Escherichia coli (STEC) are a leading cause of foodborne outbreaks of human disease, but they reside harmlessly as an asymptomatic commensal in the ruminant gut. STEC serogroup O145 are difficult to isolate as routine diagnostic methods are unable to distinguish non-O157 serogroups due to their heterogeneous metabolic characteristics, resulting in under-reporting which is likely to conceal their true prevalence. In light of these deficiencies, the purpose of this study was a twofold approach to investigate enhanced STEC O145 diagnostic culture-based methods: firstly, to use a genomic epidemiology approach to understand the genetic diversity and population structure of serogroup O145 at both a local (New Zealand) (n = 47) and global scale (n = 75) and, secondly, to identify metabolic characteristics that will help the development of a differential media for this serogroup. Analysis of a subset of E. coli serogroup O145 strains demonstrated considerable diversity in carbon utilisation, which varied in association with eae subtype and sequence type. Several carbon substrates, such as D-serine and D-malic acid, were utilised by the majority of serogroup O145 strains, which, when coupled with current molecular and culture-based methods, could aid in the identification of presumptive E. coli serogroup O145 isolates. These carbon substrates warrant subsequent testing with additional serogroup O145 strains and non-O145 strains. Serogroup O145 strains displayed extensive genetic heterogeneity that was correlated with sequence type and eae subtype, suggesting these genetic markers are good indicators for distinct E. coli phylogenetic lineages. Pangenome analysis identified a core of 3,036 genes and an open pangenome of >14,000 genes, which is consistent with the identification of distinct phylogenetic lineages. Overall, this study highlighted the phenotypic and genotypic heterogeneity within E. coli serogroup O145, suggesting that the development of a differential media targeting this serogroup will be challenging.
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Affiliation(s)
- Rose M. Collis
- AgResearch Ltd, Hopkirk Research Institute, Massey University, Palmerston North, New Zealand
- Molecular Epidemiology and Veterinary Public Health Laboratory (EpiLab), Infectious Disease Research Centre, School of Veterinary Science, Massey University, Palmerston North, New Zealand
| | - Patrick J. Biggs
- Molecular Epidemiology and Veterinary Public Health Laboratory (EpiLab), Infectious Disease Research Centre, School of Veterinary Science, Massey University, Palmerston North, New Zealand
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
- New Zealand Food Safety Science and Research Centre, Massey University, Palmerston North, New Zealand
| | - Anne C. Midwinter
- Molecular Epidemiology and Veterinary Public Health Laboratory (EpiLab), Infectious Disease Research Centre, School of Veterinary Science, Massey University, Palmerston North, New Zealand
| | - A. Springer Browne
- Molecular Epidemiology and Veterinary Public Health Laboratory (EpiLab), Infectious Disease Research Centre, School of Veterinary Science, Massey University, Palmerston North, New Zealand
| | - David A. Wilkinson
- Molecular Epidemiology and Veterinary Public Health Laboratory (EpiLab), Infectious Disease Research Centre, School of Veterinary Science, Massey University, Palmerston North, New Zealand
- New Zealand Food Safety Science and Research Centre, Massey University, Palmerston North, New Zealand
| | - Hamid Irshad
- Animal Health Programme, National Agricultural Research Centre, Islamabad, Pakistan
| | - Nigel P. French
- Molecular Epidemiology and Veterinary Public Health Laboratory (EpiLab), Infectious Disease Research Centre, School of Veterinary Science, Massey University, Palmerston North, New Zealand
- New Zealand Food Safety Science and Research Centre, Massey University, Palmerston North, New Zealand
| | - Gale Brightwell
- AgResearch Ltd, Hopkirk Research Institute, Massey University, Palmerston North, New Zealand
- New Zealand Food Safety Science and Research Centre, Massey University, Palmerston North, New Zealand
| | - Adrian L. Cookson
- AgResearch Ltd, Hopkirk Research Institute, Massey University, Palmerston North, New Zealand
- Molecular Epidemiology and Veterinary Public Health Laboratory (EpiLab), Infectious Disease Research Centre, School of Veterinary Science, Massey University, Palmerston North, New Zealand
- * E-mail:
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Carroll KJ, Harvey-Vince L, Jenkins C, Mohan K, Balasegaram S. The epidemiology of Shiga toxin-producing Escherichia coli infections in the South East of England: November 2013-March 2017 and significance for clinical and public health. J Med Microbiol 2019; 68:930-939. [PMID: 30994441 DOI: 10.1099/jmm.0.000970] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
PURPOSE This study describes the epidemiology of Shiga toxin-producing Escherichia coli (STEC) infections in a population in the South East of England. METHODS From 1 November 2013 to 31 March 2017 participating diagnostic laboratories reported Shiga toxin gene (stx) positive real-time PCR results to local public health teams. Stx positive faecal samples/isolates were referred to the Gastrointestinal Bacteria Reference Unit (GBRU) for confirmation by culture and typing by whole genome sequencing (WGS). Key clinical information was collected by public health teams.Results/Key findings. Altogether, 548 faecal specimens (420 were non-travel associated) were stx positive locally, 535 were submitted to the GBRU. STEC were isolated from 42 %, confirmed by stx PCR in 21 % and 37 % were PCR negative. The most common non-travel associated STEC serogroups were O157, O26, O146 and O91. The annualized incidence of confirmed STEC infections (PCR or culture) was 5.8 per 100 000. The ratio of O157 to non-O157 STEC serogroups was 1:7. The annualized incidence of non-O157 haemolytic uraemic syndrome-associated Escherichia coli (HUSEC) strains was 0.4 per 100 000. Bloody diarrhoea was reported by 58 % of cases infected with E. coli O157, 33 % of cases infected with non-O157 HUSEC strains and 12 % of other lower risk non-O157 strains. Overall, 76 % of non-O157 HUSEC isolates possessed the eae virulence gene. CONCLUSIONS HUSEC including serogroup O157 were uncommon and more likely to cause bloody diarrhoea than other STEC. The routine use of stx PCR testing can influence clinical management. Understanding the local epidemiology facilitates a proportionate public health response to STEC, based on clinical and microbiological characteristics including stx subtype(s).
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Affiliation(s)
- Kevin J Carroll
- 1 PHE South East, Surrey and Sussex HPT, Parkside, Chart Way, Horsham RH12 1XA, UK
| | - Lisa Harvey-Vince
- 1 PHE South East, Surrey and Sussex HPT, Parkside, Chart Way, Horsham RH12 1XA, UK
| | - Claire Jenkins
- 2 Gastrointestinal Bacteria Reference Unit, Public Health England, 61 Colindale Avenue, London NW9 5HT, UK
| | - Keerthi Mohan
- 3 PHE South East, Thames Valley HPT, Chilton, Oxon, OX11 0RQ, UK
| | - Sooria Balasegaram
- 4 Field Services, National Infection Service, Public Health England, London, UK
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Detection of Shiga toxin-producing Escherichia coli, stx1, stx2 and Salmonella by two high resolution melt curve multiplex real-time PCR. Food Control 2019. [DOI: 10.1016/j.foodcont.2018.09.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Varcasia BM, Tomassetti F, De Santis L, Di Giamberardino F, Lovari S, Bilei S, De Santis P. Presence of Shiga Toxin-Producing Escherichia coli (STEC) in Fresh Beef Marketed in 13 Regions of ITALY (2017). Microorganisms 2018; 6:E126. [PMID: 30563244 PMCID: PMC6313577 DOI: 10.3390/microorganisms6040126] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 11/30/2018] [Accepted: 12/05/2018] [Indexed: 01/02/2023] Open
Abstract
The aim of this study was to determine the prevalence of Shiga toxin-producing Escherichia coli in fresh beef marketed in 2017 in 13 regions of Italy, to evaluate the potential risk to human health. According to the ISO/TS 13136:2012 standard, 239 samples were analysed and nine were STEC positive, from which 20 strains were isolated. The STEC-positive samples were obtained from Calabria (n = 1), Campania (n = 1), Lazio (n = 2), Liguria (n = 1), Lombardia (n = 1) and Veneto (n = 3). All STEC strains were analysed for serogroups O26, O45, O55, O91, O103, O104, O111, O113, O121, O128, O145, O146 and O157, using Real-Time PCR. Three serogroups were identified amongst the 20 strains: O91 (n = 5), O113 (n = 2), and O157 (n = 1); the O-group for each of the 12 remaining STEC strains was not identified. Six stx subtypes were detected: stx1a, stx1c, stx2a, stx2b, stx2c and stx2d. Subtype stx2c was the most common, followed by stx2d and stx2b. Subtype stx2a was identified in only one eae-negative strain and occurred in combination with stx1a, stx1c and stx2b. The presence in meat of STEC strains being potentially harmful to human health shows the importance, during harvest, of implementing additional measures to reduce contamination risk.
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Affiliation(s)
- Bianca Maria Varcasia
- Istituto Zooprofilattico Sperimentale Lazio e Toscana, "M. Aleandri", 00178 Rome, Italy.
| | - Francesco Tomassetti
- Istituto Zooprofilattico Sperimentale Lazio e Toscana, "M. Aleandri", 00178 Rome, Italy.
| | - Laura De Santis
- Istituto Zooprofilattico Sperimentale Lazio e Toscana, "M. Aleandri", 00178 Rome, Italy.
| | | | - Sarah Lovari
- Istituto Zooprofilattico Sperimentale Lazio e Toscana, "M. Aleandri", 00178 Rome, Italy.
| | - Stefano Bilei
- Istituto Zooprofilattico Sperimentale Lazio e Toscana, "M. Aleandri", 00178 Rome, Italy.
| | - Paola De Santis
- Istituto Zooprofilattico Sperimentale Lazio e Toscana, "M. Aleandri", 00178 Rome, Italy.
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7
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Senthakumaran T, Brandal LT, Lindstedt BA, Jørgensen SB, Charnock C, Tunsjø HS. Implications of stx loss for clinical diagnostics of Shiga toxin-producing Escherichia coli. Eur J Clin Microbiol Infect Dis 2018; 37:2361-2370. [PMID: 30267169 DOI: 10.1007/s10096-018-3384-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Accepted: 09/18/2018] [Indexed: 12/17/2022]
Abstract
The dynamics related to the loss of stx genes from Shiga toxin-producing Escherichia coli remain unclear. Current diagnostic procedures have shortcomings in the detection and identification of STEC. This is partly owing to the fact that stx genes may be lost during an infection or in the laboratory. The aim of the present study was to provide new insight into in vivo and in vitro stx loss in order to improve diagnostic procedures. Results from the study support the theory that loss of stx is a strain-related phenomenon and not induced by patient factors. It was observed that one strain could lose stx both in vivo and in vitro. Whole genome comparison of stx-positive and stx-negative isolates from the same patient revealed that different genomic rearrangements, such as complete or partial loss of the parent prophage, may be factors in the loss of stx. Of diagnostic interest, it was shown that patients can be co-infected with different E. coli pathotypes. Therefore, identification of eae-positive, but stx-negative isolates should not be interpreted as "Shiga toxin-lost" E. coli without further testing. Growth and recovery of STEC were supported by different selective agar media for different strains, arguing for inclusion of several media in STEC diagnostics.
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Affiliation(s)
- Thulasika Senthakumaran
- Department of Multidisciplinary Laboratory Science and Medical Biochemistry, Genetic Unit, Akershus University Hospital, Lørenskog, Akershus, Norway.,Department of Life Sciences and Health, Oslo Metropolitan University, Oslo, Norway
| | - Lin Torstensen Brandal
- Department of Zoonotic, Food- and Waterborne Infections, Norwegian Institute of Public Health, Oslo, Norway
| | - Bjørn-Arne Lindstedt
- Department of Chemistry, Biotechnology and Food Sciences, Norwegian University of Life Sciences, Ås, Akershus, Norway
| | - Silje Bakken Jørgensen
- Department of Microbiology and Infection control, Akershus University Hospital, Lørenskog, Akershus, Norway
| | - Colin Charnock
- Department of Life Sciences and Health, Oslo Metropolitan University, Oslo, Norway
| | - Hege Smith Tunsjø
- Department of Life Sciences and Health, Oslo Metropolitan University, Oslo, Norway. .,Department of Microbiology and Infection control, Akershus University Hospital, Lørenskog, Akershus, Norway.
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Kiel M, Sagory-Zalkind P, Miganeh C, Stork C, Leimbach A, Sekse C, Mellmann A, Rechenmann F, Dobrindt U. Identification of Novel Biomarkers for Priority Serotypes of Shiga Toxin-Producing Escherichia coli and the Development of Multiplex PCR for Their Detection. Front Microbiol 2018; 9:1321. [PMID: 29997582 PMCID: PMC6028524 DOI: 10.3389/fmicb.2018.01321] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 05/30/2018] [Indexed: 12/22/2022] Open
Abstract
It would be desirable to have an unambiguous scheme for the typing of Shiga toxin-producing Escherichia coli (STEC) isolates to subpopulations. Such a scheme should take the high genomic plasticity of E. coli into account and utilize the stratification of STEC into subgroups, based on serotype or phylogeny. Therefore, our goal was to identify specific marker combinations for improved classification of STEC subtypes. We developed and evaluated two bioinformatic pipelines for genomic marker identification from larger sets of bacterial genome sequences. Pipeline A performed all-against-all BLASTp analyses of gene products predicted in STEC genome test sets against a set of control genomes. Pipeline B identified STEC marker genes by comparing the STEC core proteome and the "pan proteome" of a non-STEC control group. Both pipelines defined an overlapping, but not identical set of discriminative markers for different STEC subgroups. Differential marker prediction resulted from differences in genome assembly, ORF finding and inclusion cut-offs in both workflows. Based on the output of the pipelines, we defined new specific markers for STEC serogroups and phylogenetic groups frequently associated with outbreaks and cases of foodborne illnesses. These included STEC serogroups O157, O26, O45, O103, O111, O121, and O145, Shiga toxin-positive enteroaggregative E. coli O104:H4, and HUS-associated sequence type (ST)306. We evaluated these STEC marker genes for their presence in whole genome sequence data sets. Based on the identified discriminative markers, we developed a multiplex PCR (mPCR) approach for detection and typing of the targeted STEC. The specificity of the mPCR primer pairs was verified using well-defined clinical STEC isolates as well as isolates from the ECOR, DEC, and HUSEC collections. The application of the STEC mPCR for food analysis was tested with inoculated milk. In summary, we evaluated two different strategies to screen large genome sequence data sets for discriminative markers and implemented novel marker genes found in this genome-wide approach into a DNA-based typing tool for STEC that can be used for the characterization of STEC from clinical and food samples.
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Affiliation(s)
- Matthias Kiel
- Institute of Hygiene, University of Münster, Münster, Germany
| | | | - Céline Miganeh
- Genostar Bioinformatics, Montbonnot-Saint-Martin, France
| | - Christoph Stork
- Institute of Hygiene, University of Münster, Münster, Germany
| | | | | | | | | | - Ulrich Dobrindt
- Institute of Hygiene, University of Münster, Münster, Germany
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Bouvier M, Miszczycha SD, Guillarme X, Tadla C, Collinet L, Sergentet DT. Comparative Evaluation of a Novel Phage Protein Ligand Assay and Immunomagnetic Separation Method To Isolate the Seven Top Serogroups of Escherichia coli (O157, O26, O103, O145, O111, O45, and O121) in Foods at Risk. J Food Prot 2017; 80:1973-1979. [PMID: 29130763 DOI: 10.4315/0362-028x.jfp-16-479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The presence of Shiga toxin-producing Escherichia coli (STEC) in food is a major concern for food safety authorities and industries. Methods for detecting these pathogenic bacteria are crucial. Enrichment of foods for STEC identification has been optimized, but selective concentration of bacteria before isolation still needs to be improved. In the present study, we tested the performance of the VIDAS ESPT detection method against that of the immunomagnetic separation (IMS) method. A preenrichment inoculation was performed to provide a realistic scenario of the contamination that occurs in foods, and the methods were then compared. Results obtained were then confirmed in naturally contaminated foods. Preenrichment inoculation assays revealed that the novel concentration method using phage recombinant proteins or the selective capture of the target top seven STEC serogroups is as specific and sensitive as IMS. Subsequent evaluation of naturally contaminated samples confirmed that the novel concentration method and IMS are equivalent in performance under the conditions tested.
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Affiliation(s)
- M Bouvier
- 1 Research Group on Bacterial Opportunistic Pathogens and Environmental and Biological Resource Centre, Environmental Microbiology Lyon, UMR5557 Microbial Ecology, Centre National de la Recherche Scientifique, VetAgro Sup and Université Lyon 1, Villeurbanne, France; and.,2 Laboratoire d'étude des microorganismes alimentaires pathogènes, National Reference Laboratory for Shiga Toxin-Producing Escherichia coli, VetAgro Sup Campus Vétérinaire de Lyon, F-63280 Marcy L'Étoile, France
| | - S D Miszczycha
- 1 Research Group on Bacterial Opportunistic Pathogens and Environmental and Biological Resource Centre, Environmental Microbiology Lyon, UMR5557 Microbial Ecology, Centre National de la Recherche Scientifique, VetAgro Sup and Université Lyon 1, Villeurbanne, France; and
| | - X Guillarme
- 2 Laboratoire d'étude des microorganismes alimentaires pathogènes, National Reference Laboratory for Shiga Toxin-Producing Escherichia coli, VetAgro Sup Campus Vétérinaire de Lyon, F-63280 Marcy L'Étoile, France
| | - C Tadla
- 2 Laboratoire d'étude des microorganismes alimentaires pathogènes, National Reference Laboratory for Shiga Toxin-Producing Escherichia coli, VetAgro Sup Campus Vétérinaire de Lyon, F-63280 Marcy L'Étoile, France
| | - L Collinet
- 2 Laboratoire d'étude des microorganismes alimentaires pathogènes, National Reference Laboratory for Shiga Toxin-Producing Escherichia coli, VetAgro Sup Campus Vétérinaire de Lyon, F-63280 Marcy L'Étoile, France
| | - D Thevenot Sergentet
- 1 Research Group on Bacterial Opportunistic Pathogens and Environmental and Biological Resource Centre, Environmental Microbiology Lyon, UMR5557 Microbial Ecology, Centre National de la Recherche Scientifique, VetAgro Sup and Université Lyon 1, Villeurbanne, France; and.,2 Laboratoire d'étude des microorganismes alimentaires pathogènes, National Reference Laboratory for Shiga Toxin-Producing Escherichia coli, VetAgro Sup Campus Vétérinaire de Lyon, F-63280 Marcy L'Étoile, France
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10
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Castro VS, Carvalho RCT, Conte-Junior CA, Figuiredo EES. Shiga-toxin ProducingEscherichia coli: Pathogenicity, Supershedding, Diagnostic Methods, Occurrence, and Foodborne Outbreaks. Compr Rev Food Sci Food Saf 2017; 16:1269-1280. [DOI: 10.1111/1541-4337.12302] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 08/09/2017] [Accepted: 08/11/2017] [Indexed: 12/14/2022]
Affiliation(s)
- Vinicius Silva Castro
- Animal Science Program, Faculdade de Agronomia e Zootecnia; Univ. Federal de Mato Grosso; 78060-900 Mato Grosso Brazil
- Natl. Inst. of Health Quality Control; Fundação Oswaldo Cruz; Rio de Janeiro 21040-900 Rio de Janeiro Brazil
| | - Ricardo César Tavares Carvalho
- Nutrition, Food and Metabolism Program, Faculdade de Nutrição; Univ. Federal de Mato Grosso; 78060-900 Mato Grosso Brazil
| | - Carlos Adam Conte-Junior
- Dept. of Food Technology, Faculdade de Veterinária; Univ. Federal Fluminense; 24230-340 Rio de Janeiro Brazil
- Food Science Program, Inst. de Química; Univ. Federal do Rio de Janeiro; 21941-909 Rio de Janeiro Brazil
- Natl. Inst. of Health Quality Control; Fundação Oswaldo Cruz; Rio de Janeiro 21040-900 Rio de Janeiro Brazil
| | - Eduardo Eustáquio Souza Figuiredo
- Animal Science Program, Faculdade de Agronomia e Zootecnia; Univ. Federal de Mato Grosso; 78060-900 Mato Grosso Brazil
- Nutrition, Food and Metabolism Program, Faculdade de Nutrição; Univ. Federal de Mato Grosso; 78060-900 Mato Grosso Brazil
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11
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Otero V, Sánchez S, Herrera-León S, Rodríguez-Calleja JM, Otero A, García-López ML, Santos JA. Detection and characterization of Shiga toxin-producing Escherichia coli (STEC) in bulk tank ewes’ milk and sheep farm environment. Small Rumin Res 2017. [DOI: 10.1016/j.smallrumres.2017.08.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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12
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Conrad CC, Stanford K, McAllister TA, Thomas J, Reuter T. Competition during enrichment of pathogenicEscherichia colimay result in culture bias. Facets (Ott) 2017. [DOI: 10.1139/facets-2016-0007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Deadly outbreaks and illnesses due to Shiga toxin-producing Escherichia coli (STEC) occur worldwide; however, the cultivation methods required for adequate monitoring and traceback investigations are inefficient at best. Detection of STEC relies heavily on enrichment; yet no standard media or protocols exist. Furthermore, whether enrichment may bias detection of multiple STEC serogroups from complex samples is unknown. Thus, 14 STEC strains of serogroups O157 and the top six non-O157s (O26, O45, O103, O111, O121, and O145) were enriched in pairs for 6–78 h in broth and evaluated by quantitative polymerase chain reaction (qPCR). Here we show that a conventional 6-h enrichment protocol did not result in intra-species culture bias for the isolates tested. However, subsequent enrichments often produced biased cultures, with differences in the qPCR gene copy number ≥2 log10apparent in 12%, 38%, and 52% of competitions after 30, 54, and 78 h of consecutive enrichments, respectively. Some strains were able to prevail and (or) out-compete the opponent strain in 100% of competitions. Our results suggest that culture bias should be considered and (or) evaluated further due to the potential implications during routine pathogen screening and outbreak investigations.
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Affiliation(s)
- Cheyenne C. Conrad
- University of Lethbridge, Biological Sciences Department, Lethbridge, AB T1K 3M4, Canada
- Alberta Agriculture and Forestry, Lethbridge Research Centre, Lethbridge, AB T1J 4V6, Canada
- Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, AB T1J 4B1, Canada
| | - Kim Stanford
- Alberta Agriculture and Forestry, Lethbridge Research Centre, Lethbridge, AB T1J 4V6, Canada
| | - Tim A. McAllister
- Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, AB T1J 4B1, Canada
| | - James Thomas
- University of Lethbridge, Biological Sciences Department, Lethbridge, AB T1K 3M4, Canada
| | - Tim Reuter
- Alberta Agriculture and Forestry, Lethbridge Research Centre, Lethbridge, AB T1J 4V6, Canada
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Elder JR, Bugarel M, den Bakker HC, Loneragan GH, Nightingale KK. Interrogation of single nucleotide polymorphisms in gnd provides a novel method for molecular serogrouping of clinically important Shiga toxin producing Escherichia coli (STEC) targeted by regulation in the United States, including the "big six" non-O157 STEC and STEC O157. J Microbiol Methods 2016; 129:85-93. [PMID: 27432340 DOI: 10.1016/j.mimet.2016.07.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 07/06/2016] [Accepted: 07/07/2016] [Indexed: 12/22/2022]
Abstract
Escherichia coli O157:H7 has frequently been associated with foodborne infections and is considered an adulterant in raw non-intact beef in the U.S. Shiga toxin-producing E. coli (STEC) belonging to serogroups O26, O45, O103, O111, O121, and O145 (known as the "big six" non-O157) were estimated to cause >70% of foodborne infections attributed to non-O157 serogroups in the U.S., as a result, these six serogroups have also been targeted by regulation in the U.S. The purpose of this study was to develop a rapid and high-throughput molecular method to group STEC isolates into seven clinically important serogroups (i.e., O157 and the "big six" non-O157 serogroups) targeted by regulation in the U.S. by interrogating single nucleotide polymorphisms (SNPs) in gnd. A collection of 195 STEC isolates, including isolates belonging to O157:H7 (n=18), O26 (n=21), O45 (n=19), O103 (n=24), O111 (n=24), O121 (n=23), O145 (n=21), and ten other STEC serogroups (n=45), was assembled and characterized by full gnd sequencing to identify informative SNPs for molecular serogrouping. A multiplex SNP typing assay was developed to interrogate twelve informative gnd SNPs by single base pair extension chemistry and used to characterize the STEC isolate collection assembled here. SNP types were assigned to each isolate by the assay and polymorphisms were confirmed with gnd sequence data. O-serogroup-specific SNP types were identified for each of the seven clinically important STEC serogroups, which allowed the differentiation of these seven STEC serogroups from other non-O157 STEC serogroups. Although serogroups of the "big six" non-O157 STEC and O157:H7 contained multiple SNP types per O-serogroup, there were no overlapping SNP types between serogroups. Our results demonstrate that molecular serogrouping of STEC isolates by interrogation of informative SNPs in gnd represents an alternative to traditional serogrouping by agglutination for rapid and high-throughput identification of clinically important STEC serogroups targeted by regulation for surveillance and epidemiological investigations.
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Affiliation(s)
- J R Elder
- Department of Food and Animal Sciences, Texas Tech University, Lubbock, TX 79409, United States; Department of Animal Sciences, Colorado State University, Fort Collins, CO 80523, United States
| | - M Bugarel
- Department of Food and Animal Sciences, Texas Tech University, Lubbock, TX 79409, United States
| | - H C den Bakker
- Department of Food and Animal Sciences, Texas Tech University, Lubbock, TX 79409, United States; Department of Food Science and Technology, Cornell University, Ithaca, NY 14853, United States
| | - G H Loneragan
- Department of Food and Animal Sciences, Texas Tech University, Lubbock, TX 79409, United States
| | - K K Nightingale
- Department of Food and Animal Sciences, Texas Tech University, Lubbock, TX 79409, United States; Department of Animal Sciences, Colorado State University, Fort Collins, CO 80523, United States.
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14
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Carter JM, Lin A, Clotilde L, Lesho M. Rapid, Multiplexed Characterization of Shiga Toxin-Producing Escherichia coli (STEC) Isolates Using Suspension Array Technology. Front Microbiol 2016; 7:439. [PMID: 27242670 PMCID: PMC4873620 DOI: 10.3389/fmicb.2016.00439] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 03/18/2016] [Indexed: 01/03/2023] Open
Abstract
Molecular methods have emerged as the most reliable techniques to detect and characterize pathogenic Escherichia coli. These molecular techniques include conventional single analyte and multiplex PCR, PCR followed by microarray detection, pulsed-field gel electrophoresis (PFGE), and whole genome sequencing. The choice of methods used depends upon the specific needs of the particular study. One versatile method involves detecting serogroup-specific markers by hybridization or binding to encoded microbeads in a suspension array. This molecular serotyping method has been developed and adopted for investigating E. coli outbreaks. The major advantages of this technique are the ability to simultaneously serotype E. coli and detect the presence of virulence and pathogenicity markers. Here, we describe the development of a family of multiplex molecular serotyping methods for Shiga toxin-producing E. coli, compare their performance to traditional serotyping methods, and discuss the cost-benefit balance of these methods in the context of various food safety objectives.
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Affiliation(s)
- John M. Carter
- Pacific West Area – Western Regional Research Center – Produce Safety and Microbiology Research, Agricultural Research Service, United States Department of Agriculture, Albany, CAUSA
| | - Andrew Lin
- ORA/PA-FO/SAN-LB – Office of Global Regulatory Operations and Policy – Oceans, Reefs & Aquariums – Food and Drug Administration, United States Department of Health and Human Services, Alameda, CAUSA
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15
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Abstract
Shiga toxin-producing Escherichia coli (STEC) strains are commonly found in the intestine of ruminant species of wild and domestic animals. Excretion of STEC with animal feces results in a broad contamination of food and the environment. Humans get infected with STEC through ingestion of contaminated food, by contact with the environment, and from STEC-excreting animals and humans. STEC strains can behave as human pathogens, and some of them, called enterohemorrhagic E. coli (EHEC), may cause hemorrhagic colitis (HC) and hemolytic-uremic syndrome (HUS). Because of the diversity of STEC types, detection strategies for STEC and EHEC are based on the identification of Shiga toxins or the underlying genes. Cultural enrichment of STEC from test samples is needed for identification, and different protocols were developed for this purpose. Multiplex real-time PCR protocols (ISO/CEN TS13136 and USDA/FSIS MLG5B.01) have been developed to specifically identify EHEC by targeting the LEE (locus of enterocyte effacement)-encoded eae gene and genes for EHEC-associated O groups. The employment of more genetic markers (nle and CRISPR) is a future challenge for better identification of EHEC from any kinds of samples. The isolation of STEC or EHEC from a sample is required for confirmation, and different cultivation protocols and media for this purpose have been developed. Most STEC strains present in food, animals, and the environment are eae negative, but some of these strains can cause HC and HUS in humans as well. Phenotypic assays and molecular tools for typing EHEC and STEC strains are used to detect and characterize human pathogenic strains among members of the STEC group.
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16
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17
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Shridhar PB, Noll LW, Shi X, An B, Cernicchiaro N, Renter DG, Nagaraja TG, Bai J. Multiplex Quantitative PCR Assays for the Detection and Quantification of the Six Major Non-O157 Escherichia coli Serogroups in Cattle Feces. J Food Prot 2016; 79:66-74. [PMID: 26735031 DOI: 10.4315/0362-028x.jfp-15-319] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Shiga toxin-producing Escherichia coli (STEC) serogroups O26, O45, O103, O111, O121, and O145, called non-O157 STEC, are important foodborne pathogens. Cattle, a major reservoir, harbor the organisms in the hindgut and shed them in the feces. Although limited data exist on fecal shedding, concentrations of non-O157 STEC in feces have not been reported. The objectives of our study were (i) to develop and validate two multiplex quantitative PCR (mqPCR) assays, targeting O-antigen genes of O26, O103, and O111 (mqPCR-1) and O45, O121, and O145 (mqPCR-2); (ii) to utilize the two assays, together with a previously developed four-plex qPCR assay (mqPCR-3) targeting the O157 antigen and three virulence genes (stx1, stx2, and eae), to quantify seven serogroups and three virulence genes in cattle feces; and (iii) to compare the three mqPCR assays to a 10-plex conventional PCR (cPCR) targeting seven serogroups and three virulence genes and culture methods to detect seven E. coli serogroups in cattle feces. The two mqPCR assays (1 and 2) were shown to be specific to the target genes, and the detection limits were 4 and 2 log CFU/g of pure culture-spiked fecal samples, before and after enrichment, respectively. A total of 576 fecal samples collected from a feedlot were enriched in E. coli broth and were subjected to quantification (before enrichment) and detection (after enrichment). Of the 576 fecal samples subjected, before enrichment, to three mqPCR assays for quantification, 175 (30.4%) were quantifiable (≥4 log CFU/g) for at least one of the seven serogroups, with O157 being the most common serogroup. The three mqPCR assays detected higher proportions of postenriched fecal samples (P > 0.01) as positive for one or more serogroups compared with cPCR and culture methods. This is the first study to assess the applicability of qPCR assays to detect and quantify six non-O157 serogroups in cattle feces and to generate data on fecal concentration of the six serogroups.
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Affiliation(s)
- P B Shridhar
- Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, Kansas 66506, USA
| | - L W Noll
- Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, Kansas 66506, USA
| | - X Shi
- Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, Kansas 66506, USA
| | - B An
- Veterinary Diagnostic Laboratory, Kansas State University, Manhattan, Kansas 66506, USA
| | - N Cernicchiaro
- Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, Kansas 66506, USA
| | - D G Renter
- Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, Kansas 66506, USA
| | - T G Nagaraja
- Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, Kansas 66506, USA.
| | - J Bai
- Veterinary Diagnostic Laboratory, Kansas State University, Manhattan, Kansas 66506, USA.
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18
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Brusa V, Galli L, Linares LH, Ortega EE, Lirón JP, Leotta GA. Development and validation of two SYBR green PCR assays and a multiplex real-time PCR for the detection of Shiga toxin-producing Escherichia coli in meat. J Microbiol Methods 2015; 119:10-7. [PMID: 26410309 DOI: 10.1016/j.mimet.2015.09.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Revised: 09/22/2015] [Accepted: 09/23/2015] [Indexed: 11/18/2022]
Abstract
Shiga toxin-producing Escherichia coli (STEC) are recognized as food-borne pathogens. We developed and validated two SYBR green PCR (SYBR-PCR) and a real-time multiplex PCR (RT-PCR) to detect stx1 and stx2 genes in meat samples, and compared these techniques in ground beef samples from retail stores. One set of primers and one hydrolysis probe were designed for each stx gene. For RT-PCR, an internal amplification control (IAC) was used. All PCR intra-laboratory validations were performed using pure strains and artificially contaminated ground beef samples. A total of 50 STEC and 30 non-STEC strains were used. Naturally contaminated ground beef samples (n=103) were obtained from retail stores and screened with SYBR-PCR and RT-PCR, and stx-positive samples were processed for STEC isolation. In the intra-laboratory validation, each PCR obtained a 1×10(2) CFU mL(-1) limit of detection and 100% inclusivity and exclusivity. The same results were obtained when different laboratory analysts in alternate days performed the assay. The level of agreement obtained with SYBR-PCR and RT-PCR was kappa=0.758 and 0.801 (P<0.001) for stx1 and stx2 gene detection, respectively. Two PCR strategies were developed and validated, and excellent performance with artificially contaminated ground beef samples was obtained. However, the efforts made to isolate STEC from retail store samples were not enough. Only 11 STEC strains were isolated from 35 stx-positive ground beef samples identically detected by all PCRs. The combination of molecular approaches based on the identification of a virulence genotypic profile of STEC must be considered to improve isolation.
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Affiliation(s)
- Victoria Brusa
- Laboratorio de Microbiología de Alimentos, Facultad de Ciencias Veterinarias, UNLP, La Plata, Argentina; IGEVET - Instituto de Genética Veterinaria "Ing. Fernando N. Dulout" (UNLP-CONICET LA PLATA), Facultad de Ciencias Veterinarias, UNLP La Plata, Argentina
| | - Lucía Galli
- IGEVET - Instituto de Genética Veterinaria "Ing. Fernando N. Dulout" (UNLP-CONICET LA PLATA), Facultad de Ciencias Veterinarias, UNLP La Plata, Argentina
| | - Luciano H Linares
- Laboratorio de Microbiología de Alimentos, Facultad de Ciencias Veterinarias, UNLP, La Plata, Argentina
| | - Emanuel E Ortega
- Laboratorio de Microbiología de Alimentos, Facultad de Ciencias Veterinarias, UNLP, La Plata, Argentina
| | - Juan P Lirón
- IGEVET - Instituto de Genética Veterinaria "Ing. Fernando N. Dulout" (UNLP-CONICET LA PLATA), Facultad de Ciencias Veterinarias, UNLP La Plata, Argentina
| | - Gerardo A Leotta
- IGEVET - Instituto de Genética Veterinaria "Ing. Fernando N. Dulout" (UNLP-CONICET LA PLATA), Facultad de Ciencias Veterinarias, UNLP La Plata, Argentina.
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19
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Singh P, Mustapha A. Multiplex real-time PCR assays for detection of eight Shiga toxin-producing Escherichia coli in food samples by melting curve analysis. Int J Food Microbiol 2015; 215:101-8. [PMID: 26355415 DOI: 10.1016/j.ijfoodmicro.2015.08.022] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 08/25/2015] [Accepted: 08/28/2015] [Indexed: 11/18/2022]
Abstract
Shiga toxin-producing Escherichia coli (STEC) are pathogenic strains of E. coli that can cause bloody diarrhea and kidney failure. Seven STEC serogroups, O157, O26, O45, O103, O111, O121 and O145 are responsible for more than 71% of the total infections caused by this group of pathogens. All seven serogroups are currently considered as adulterants in non-intact beef products in the U.S. In this study, two multiplex melt curve real-time PCR assays with internal amplification controls (IACs) were standardized for the detection of eight STEC serogroups. The first multiplex assay targeted E. coli serogroups O145, O121, O104, and O157; while the second set detected E. coli serogroups O26, O45, O103 and O111. The applicability of the assays was tested using 11 different meat and produce samples. For food samples spiked with a cocktail of four STEC serogroups with a combined count of 10 CFU/25 g food, all targets of the multiplex assays were detected after an enrichment period of 6h. The assays also worked efficiently when 325 g of food samples were spiked with 10 CFU of STECs. The assays are not dependent on fluorescent-labeled probes or immunomagnetic beads, and can be used for the detection of eight STEC serogroups in less than 11h. Routine preliminary screening of STECs in food samples is performed by testing for the presence of STEC virulence genes. The assays developed in this study can be useful as a first- or second-tier test for the identification of the eight O serogroup-specific genes in suspected food samples.
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Affiliation(s)
- Prashant Singh
- Food Science Program, University of Missouri, Columbia, USA
| | - Azlin Mustapha
- Food Science Program, University of Missouri, Columbia, USA.
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20
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Beutin L, Delannoy S, Fach P. Sequence Variations in the Flagellar Antigen Genes fliCH25 and fliCH28 of Escherichia coli and Their Use in Identification and Characterization of Enterohemorrhagic E. coli (EHEC) O145:H25 and O145:H28. PLoS One 2015; 10:e0126749. [PMID: 26000885 PMCID: PMC4441469 DOI: 10.1371/journal.pone.0126749] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 04/07/2015] [Indexed: 11/19/2022] Open
Abstract
Enterohemorrhagic E. coli (EHEC) serogroup O145 is regarded as one of the major EHEC serogroups involved in severe infections in humans. EHEC O145 encompasses motile and non-motile strains of serotypes O145:H25 and O145:H28. Sequencing the fliC-genes associated with the flagellar antigens H25 and H28 revealed the genetic diversity of the fliCH25 and fliCH28 gene sequences in E. coli. Based on allele discrimination of these fliC-genes real-time PCR tests were designed for identification of EHEC O145:H25 and O145:H28. The fliCH25 genes present in O145:H25 were found to be very similar to those present in E. coli serogroups O2, O100, O165, O172 and O177 pointing to their common evolution but were different from fliCH25 genes of a multiple number of other E. coli serotypes. In a similar way, EHEC O145:H28 harbor a characteristic fliCH28 allele which, apart from EHEC O145:H28, was only found in enteropathogenic (EPEC) O28:H28 strains that shared some common traits with EHEC O145:H28. The real time PCR-assays targeting these fliCH25[O145] and fliCH28[O145] alleles allow better characterization of EHEC O145:H25 and EHEC O145:H28. Evaluation of these PCR assays in spiked ready-to eat salad samples resulted in specific detection of both types of EHEC O145 strains even when low spiking levels of 1-10 cfu/g were used. Furthermore these PCR assays allowed identification of non-motile E. coli strains which are serologically not typable for their H-antigens. The combined use of O-antigen genotyping (O145wzy) and detection of the respective fliCH25[O145] and fliCH28[O145] allele types contributes to improve identification and molecular serotyping of E. coli O145 isolates.
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Affiliation(s)
- Lothar Beutin
- National Reference Laboratory for Escherichia coli, Federal Institute for Risk Assessment (BfR), Diedersdorfer Weg 1, D-12277, Berlin, Germany
| | - Sabine Delannoy
- Université Paris-Est, Anses (French Agency for Food, Environmental and Occupational Health and Safety), Food Safety Laboratory, IdentyPath platform, 14 rue Pierre et Marie Curie, Fr-94700, Maisons-Alfort, France
| | - Patrick Fach
- Université Paris-Est, Anses (French Agency for Food, Environmental and Occupational Health and Safety), Food Safety Laboratory, IdentyPath platform, 14 rue Pierre et Marie Curie, Fr-94700, Maisons-Alfort, France
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21
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Genetic Diversity of the fliC Genes Encoding the Flagellar Antigen H19 of Escherichia coli and Application to the Specific Identification of Enterohemorrhagic E. coli O121:H19. Appl Environ Microbiol 2015; 81:4224-30. [PMID: 25862232 DOI: 10.1128/aem.00591-15] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 04/09/2015] [Indexed: 11/20/2022] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) O121:H19 belong to a specific clonal type distinct from other classical EHEC and major enteropathogenic E. coli groups and is regarded as one of the major EHEC serogroups involved in severe infections in humans. Sequencing of the fliC genes associated with the flagellar antigen H19 (fliCH19) revealed the genetic diversity of the fliCH19 gene sequences in E. coli. A cluster analysis of 12 fliCH19 sequences, 4 from O121 and 8 from non-O121 E. coli strains, revealed five different genotypes. All O121:H19 strains fell into one cluster, whereas a second cluster was formed by five non-O121:H19 strains. Cluster 1 and cluster 2 strains differ by 27 single nucleotide exchanges in their fliCH19 genes (98.5% homology). Based on allele discrimination of the fliCH19 genes, a real-time PCR test was designed for specific identification of EHEC O121:H19. The O121 fliCH19 PCR tested negative in 73 E. coli H19 strains that belonged to serogroups other than O121, including 28 different O groups, O-nontypeable H19, and O-rough:H19 strains. The O121 fliCH19 PCR reacted with all 16 tested O121:H19 strains and 1 O-rough:H19 strain which was positive for the O121 wzx gene. A cross-reaction was observed only with E. coli H32 strains which share sequence similarities in the target region of the O121 fliCH19 PCR. The combined use of O-antigen genotyping (O121 wzx) and the detection of O121 fliCH19 allele type contributes to improving the identification and molecular serotyping of EHEC O121:H19 motile and nonmotile strains and variants of these strains lacking stx genes.
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Further development of sample preparation and detection methods for O157 and the top 6 non-O157 STEC serogroups in cattle feces. J Microbiol Methods 2014; 105:22-30. [DOI: 10.1016/j.mimet.2014.06.020] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 06/26/2014] [Indexed: 11/22/2022]
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Molecular detection of nine clinically important non-O157 Escherichia coli serogroups from raw sheep meat in Chaharmahal-va-Bakhtiari province, Iran. Meat Sci 2014; 97:428-32. [PMID: 24769098 DOI: 10.1016/j.meatsci.2014.02.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2013] [Revised: 02/02/2014] [Accepted: 02/05/2014] [Indexed: 11/21/2022]
Abstract
STEC isolates and also stx-negative Escherichia coli isolates from sheep meat from the Chaharmahal-va-Bakhtiari province, Iran were analyzed for nine clinically important non-O157 serotypes by PCR. A total of 90 E. coli isolates were tested. Stx-positive and eae-positive E. coli isolates did not belong to the nine most clinically relevant non-O157 STECs. Of the 80 non-STEC isolates, two belonged to the O103 and two belonged to the O128 groups. Stx-negative E. coli O103 and O128 strains isolated have potential in acquiring stx genes and continuing into the digestive system of consumers. Further studies are needed to analyze virulence characteristics of these E. coli strains to determine their potential role in causing disease in humans. For the sake of public health, it is important to monitor and investigate non-O157 diarrheagenic E. coli strains in meat in order to control and prevent them.
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24
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Lorenz SC, Son I, Maounounen-Laasri A, Lin A, Fischer M, Kase JA. Prevalence of hemolysin genes and comparison of ehxA subtype patterns in Shiga toxin-producing Escherichia coli (STEC) and non-STEC strains from clinical, food, and animal sources. Appl Environ Microbiol 2013; 79:6301-11. [PMID: 23934487 PMCID: PMC3811216 DOI: 10.1128/aem.02200-13] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 07/30/2013] [Indexed: 11/20/2022] Open
Abstract
Shiga toxin-producing Escherichia coli (STEC) belonging to certain serogroups (e.g., O157 and O26) can cause serious conditions like hemolytic-uremic syndrome (HUS), but other strains might be equally pathogenic. While virulence factors, like stx and eae, have been well studied, little is known about the prevalence of the E. coli hemolysin genes (hlyA, ehxA, e-hlyA, and sheA) in association with these factors. Hemolysins are potential virulence factors, and ehxA and hlyA have been associated with human illness, but the significance of sheA is unknown. Hence, 435 E. coli strains belonging to 62 different O serogroups were characterized to investigate gene presence and phenotypic expression of hemolysis. We further investigated ehxA subtype patterns in E. coli isolates from clinical, animal, and food sources. While sheA and ehxA were widely distributed, e-hlyA and hlyA were rarely found. Most strains (86.7%) were hemolytic, and significantly more hemolytic (95%) than nonhemolytic strains (49%) carried stx and/or eae (P < 0.0001). ehxA subtyping, as performed by using PCR in combination with restriction fragment length polymorphism analysis, resulted in six closely related subtypes (>94.2%), with subtypes A/D being eae-negative STECs and subtypes B, C, E, and F eae positive. Unexpectedly, ehxA subtype patterns differed significantly between isolates collected from different sources (P < 0.0001), suggesting that simple linear models of exposure and transmission need modification; animal isolates carried mostly subtypes A/C (39.3%/42.9%), food isolates carried mainly subtype A (81.9%), and clinical isolates carried mainly subtype C (66.4%). Certain O serogroups correlated with particular ehxA subtypes: subtype A with O104, O113, and O8; B exclusively with O157; C with O26, O111, and O121.
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Affiliation(s)
- Sandra C. Lorenz
- U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Microbiology, College Park, Maryland, USA
- University of Hamburg, Hamburg School of Food Science, Institute of Food Chemistry, Hamburg, Germany
| | - Insook Son
- U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Microbiology, College Park, Maryland, USA
| | - Anna Maounounen-Laasri
- U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Microbiology, College Park, Maryland, USA
| | - Andrew Lin
- U.S. Food and Drug Administration, San Francisco District Laboratory, Alameda, California, USA
| | - Markus Fischer
- University of Hamburg, Hamburg School of Food Science, Institute of Food Chemistry, Hamburg, Germany
| | - Julie A. Kase
- U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Microbiology, College Park, Maryland, USA
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25
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Wang F, Yang Q, Kase JA, Meng J, Clotilde LM, Lin A, Ge B. Current trends in detecting non-O157 Shiga toxin-producing Escherichia coli in food. Foodborne Pathog Dis 2013; 10:665-77. [PMID: 23755895 DOI: 10.1089/fpd.2012.1448] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Non-O157 Shiga toxin-producing Escherichia coli (non-O157 STEC) strains are increasingly recognized as important foodborne pathogens worldwide. Together with E. coli O157:H7, six additional STEC serogroups (O26, O45, O103, O111, O121, and O145) are now regulated as adulterants in certain raw beef products in the United States. However, effective detection and isolation of non-O157 STEC strains from food matrices remain challenging. In the past decade, great attention has been paid to developing rapid and reliable detection methods for STEC in general (targeting common virulence factors) and specific STEC serogroups in particular (targeting serogroup-specific traits). This review summarizes current trends in detecting non-O157 STEC in food, including culture, immunological, and molecular methods, as well as several novel technologies.
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Affiliation(s)
- Fei Wang
- Department of Food Science, Louisiana State University Agricultural Center , Baton Rouge, Louisiana, USA
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Lin A, Kase JA, Moore MM, Son I, Tran N, Clotilde LM, Jarvis K, Jones K, Kasturi K, Nabe K, Nucci M, Wagley GS, Wang F, Ge B, Hammack TS. Multilaboratory validation of a luminex microbead-based suspension array for the identification of the 11 most clinically relevant Shiga toxin-producing Escherichia coli O serogroups. J Food Prot 2013; 76:867-70. [PMID: 23643130 DOI: 10.4315/0362-028x.jfp-12-468] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Rapid and high-throughput identification and serotyping of Shiga toxin-producing Escherichia coli (STEC) O serogroups is important for detecting, investigating, and controlling STEC infection outbreaks and removing hazardous products from commerce. A Luminex microbead-based suspension array has been developed to identify the 11 most clinically relevant STEC serogroups: O26, O45, O91, O103, O104, O111, O113, O121, O128, O145, and O157. Here we present results of a blinded multilaboratory collaborative study involving 10 participants from nine laboratories using 55 unknown strains. From the total 495 analyses, two false-positive and three false-negative results were obtained, indicating the assay to be a rapid, high-throughput, and robust method for identifying clinically relevant STEC serogroups.
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Affiliation(s)
- Andrew Lin
- U.S. Food and Drug Administration, San Francisco District, Alameda, California 94502, USA.
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Magwedere K, Dang HA, Mills EW, Cutter CN, Roberts EL, DebRoy C. Incidence of Shiga toxin–producing Escherichia coli strains in beef, pork, chicken, deer, boar, bison, and rabbit retail meat. J Vet Diagn Invest 2013; 25:254-8. [DOI: 10.1177/1040638713477407] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The objective of the current study was to determine the incidence of contamination by the top 7 Shiga toxin–producing Escherichia coli (STEC) O-groups, responsible for the majority of E. coli infections in human beings, in retail meat from different animal species. Samples from ground beef ( n = 51), ground pork ( n = 16), ground chicken ( n = 16), and game meat (deer, wild boar, bison, and rabbit; n = 55) were collected from retail vendors for the detection of 7 STEC O-groups (O26, O45, O103, O111, O121, O145, and O157). Meat samples were tested by using a multiplex polymerase chain reaction assay targeting the wzx gene of O antigen gene clusters of the 7 STEC O-groups. The positive samples were further tested for Shiga toxin genes ( stx1 and stx2). Out of a total of 83 ground beef, pork, and chicken samples, 17 (20%) carried O121, 9 (10%) carried O45, 8 (9%) carried O157, 3 (3%) carried O103, and 1 (1%) carried O145. None of the samples were positive for O26, O111, or the stx gene. All 3 white-tailed deer samples (100%) were positive for O45, O103, or both, 2 (10%) out of 20 red deer samples exhibited the presence of O103, and all 3 bison samples were contaminated with either O121, O145, or O157. One sample from ground deer, contaminated with E. coli O45, carried the stx1 gene. This preliminary investigation illustrates the importance of microbiological testing of pathogens in meat products, as well as the recognized need for increased surveillance and research on foodborne pathogens.
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Affiliation(s)
- Kudakwashe Magwedere
- Departments of Veterinary and Biomedical Sciences (Dang, Roberts, DebRoy), Pennsylvania State University, University Park, PA
- Animal Science (Magwedere, Mills), Pennsylvania State University, University Park, PA
- Food Science (Cutter), Pennsylvania State University, University Park, PA
| | - Huu Anh Dang
- Departments of Veterinary and Biomedical Sciences (Dang, Roberts, DebRoy), Pennsylvania State University, University Park, PA
- Animal Science (Magwedere, Mills), Pennsylvania State University, University Park, PA
- Food Science (Cutter), Pennsylvania State University, University Park, PA
| | - Edward W. Mills
- Departments of Veterinary and Biomedical Sciences (Dang, Roberts, DebRoy), Pennsylvania State University, University Park, PA
- Animal Science (Magwedere, Mills), Pennsylvania State University, University Park, PA
- Food Science (Cutter), Pennsylvania State University, University Park, PA
| | - Catherine N. Cutter
- Departments of Veterinary and Biomedical Sciences (Dang, Roberts, DebRoy), Pennsylvania State University, University Park, PA
- Animal Science (Magwedere, Mills), Pennsylvania State University, University Park, PA
- Food Science (Cutter), Pennsylvania State University, University Park, PA
| | - Elisabeth L. Roberts
- Departments of Veterinary and Biomedical Sciences (Dang, Roberts, DebRoy), Pennsylvania State University, University Park, PA
- Animal Science (Magwedere, Mills), Pennsylvania State University, University Park, PA
- Food Science (Cutter), Pennsylvania State University, University Park, PA
| | - Chitrita DebRoy
- Departments of Veterinary and Biomedical Sciences (Dang, Roberts, DebRoy), Pennsylvania State University, University Park, PA
- Animal Science (Magwedere, Mills), Pennsylvania State University, University Park, PA
- Food Science (Cutter), Pennsylvania State University, University Park, PA
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Farrokh C, Jordan K, Auvray F, Glass K, Oppegaard H, Raynaud S, Thevenot D, Condron R, De Reu K, Govaris A, Heggum K, Heyndrickx M, Hummerjohann J, Lindsay D, Miszczycha S, Moussiegt S, Verstraete K, Cerf O. Review of Shiga-toxin-producing Escherichia coli (STEC) and their significance in dairy production. Int J Food Microbiol 2013; 162:190-212. [DOI: 10.1016/j.ijfoodmicro.2012.08.008] [Citation(s) in RCA: 179] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 07/31/2012] [Accepted: 08/01/2012] [Indexed: 01/08/2023]
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Miszczycha SD, Perrin F, Ganet S, Jamet E, Tenenhaus-Aziza F, Montel MC, Thevenot-Sergentet D. Behavior of different Shiga toxin-producing Escherichia coli serotypes in various experimentally contaminated raw-milk cheeses. Appl Environ Microbiol 2013; 79:150-8. [PMID: 23087038 PMCID: PMC3536096 DOI: 10.1128/aem.02192-12] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 10/08/2012] [Indexed: 02/07/2023] Open
Abstract
Shiga toxin-producing Escherichia coli (STEC) is an important cause of food-borne illness. The public health implication of the presence of STEC in dairy products remains unclear. Knowledge of STEC behavior in cheeses would help to evaluate the human health risk. The aim of our study was to observe the growth and survival of experimentally inoculated STEC strains in raw-milk cheeses manufactured and ripened according to five technological schemes: blue-type cheese, uncooked pressed cheese with long ripening and with short ripening steps, cooked cheese, and lactic cheese. Cheeses were contaminated with different STEC serotypes (O157:H7, O26:H11, O103:H2, and O145:H28) at the milk preparation stage. STEC growth and survival were monitored on selective media during the entire manufacturing process. STEC grew (2 to 3 log(10) CFU · g(-1)) in blue-type cheese and the two uncooked pressed cheeses during the first 24 h of cheese making. Then, STEC levels progressively decreased in cheeses that were ripened for more than 6 months. In cooked cheese and in lactic cheese with a long acidic coagulation step (pH < 4.5), STEC did not grow. Their levels decreased after the cooking step in the cooked cheese and after the coagulation step in the lactic cheese, but STEC was still detectable at the end of ripening and storage. A serotype effect was found: in all cheeses studied, serotype O157:H7 grew less strongly and was less persistent than the others serotypes. This study improves knowledge of the behavior of different STEC serotypes in various raw-milk cheeses.
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Affiliation(s)
- Stéphane D. Miszczycha
- Université de Lyon, CALITYSS-EMSA-VetAgro Sup, Campus Vétérinaire de Lyon, Marcy l'Etoile, France
- Centre National de l'Interprofession et de l'Economie Laitière (CNIEL), Paris, France
| | | | - Sarah Ganet
- Université de Lyon, CALITYSS-EMSA-VetAgro Sup, Campus Vétérinaire de Lyon, Marcy l'Etoile, France
- LMAP-NRL STEC-VetAgro Sup, Campus Vétérinaire de Lyon, Marcy l'Etoile, France
| | | | - Fanny Tenenhaus-Aziza
- Centre National de l'Interprofession et de l'Economie Laitière (CNIEL), Paris, France
| | | | - Delphine Thevenot-Sergentet
- Université de Lyon, CALITYSS-EMSA-VetAgro Sup, Campus Vétérinaire de Lyon, Marcy l'Etoile, France
- LMAP-NRL STEC-VetAgro Sup, Campus Vétérinaire de Lyon, Marcy l'Etoile, France
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Conrad CC, Gilroyed BH, McAllister TA, Reuter T. Synthesis of O-serogroup specific positive controls and real-time PCR standards for nine clinically relevant non-O157 STECs. J Microbiol Methods 2012; 91:52-6. [DOI: 10.1016/j.mimet.2012.07.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 07/05/2012] [Accepted: 07/05/2012] [Indexed: 10/28/2022]
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Subtilase cytotoxin encoding genes are present in human, sheep and deer intimin-negative, Shiga toxin-producing Escherichia coli O128:H2. Vet Microbiol 2012; 159:531-5. [DOI: 10.1016/j.vetmic.2012.04.036] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 04/25/2012] [Accepted: 04/27/2012] [Indexed: 01/20/2023]
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32
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Kolesnikov AV, Kozyr’ AV, Shemyakin IG. The prospects for using aptamers in diagnosing bacterial infections. MOLECULAR GENETICS MICROBIOLOGY AND VIROLOGY 2012. [DOI: 10.3103/s0891416812020048] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Rapid and specific detection of escherichia coli serogroups O26, O45, O103, O111, O121, O145, and O157 in ground beef, beef trim, and produce by loop-mediated isothermal amplification. Appl Environ Microbiol 2012; 78:2727-36. [PMID: 22327594 DOI: 10.1128/aem.07975-11] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli O157 and six additional serogroups of Shiga toxin-producing E. coli (STEC) (O26, O45, O103, O111, O121, and O145) account for the majority of STEC infections in the United States. In this study, O serogroup-specific genes (wzx or wzy) were used to design loop-mediated isothermal amplification (LAMP) assays for the rapid and specific detection of these leading STEC serogroups. The assays were evaluated in pure culture and spiked food samples (ground beef, beef trim, lettuce, and spinach) and compared with real-time quantitative PCR (qPCR). No false-positive or false-negative results were observed among 120 bacterial strains used to evaluate assay specificity. The limits of detection of various STEC strains belonging to these target serogroups were approximately 1 to 20 CFU/reaction mixture in pure culture and 10(3) to 10(4) CFU/g in spiked food samples, which were comparable to those of qPCR. Standard curves generated suggested good linear relationships between STEC cell numbers and LAMP turbidity signals. In various beef and produce samples spiked with two low levels (1 to 2 and 10 to 20 CFU/25 g) of respective STEC strains, the LAMP assays consistently achieved accurate detection after 6 to 8 h of enrichment. In conclusion, these newly developed LAMP assays may facilitate rapid and reliable detection of the seven major STEC serogroups in ground beef, beef trim, and produce during routine sample testing.
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López-Campos G, Martínez-Suárez JV, Aguado-Urda M, López-Alonso V. Detection, Identification, and Analysis of Foodborne Pathogens. SPRINGERBRIEFS IN FOOD, HEALTH, AND NUTRITION 2012. [DOI: 10.1007/978-1-4614-3250-0_2] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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35
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Molecular serogrouping of porcine enterotoxigenic Escherichia coli from Australia. J Microbiol Methods 2011; 88:73-6. [PMID: 22093999 DOI: 10.1016/j.mimet.2011.10.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Accepted: 10/20/2011] [Indexed: 11/23/2022]
Abstract
Enterotoxigenic Escherichia coli (ETEC) is a common etiological agent of neonatal, pre and post weaning diarrhoea in piglets. One of the most important steps in the diagnosis and epidemiological understanding of this organism is accurate serogrouping. In many instances, however, conventional serogrouping fails to produce accurate identification of serogroups. In this communication we report a modified and simplified molecular serogrouping method (rfb-RFLP) for the accurate identification of the most common porcine ETEC strains that cause neonatal, pre and post weaning diarrhoea in Australia.
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Lin A, Nguyen L, Lee T, Clotilde LM, Kase JA, Son I, Carter JM, Lauzon CR. Rapid O serogroup identification of the ten most clinically relevant STECs by Luminex microbead-based suspension array. J Microbiol Methods 2011; 87:105-10. [DOI: 10.1016/j.mimet.2011.07.019] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 07/19/2011] [Accepted: 07/21/2011] [Indexed: 11/25/2022]
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