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McMahon T, Clarke S, Deschênes M, Tapp K, Blais B, Gill A. Real-time PCR primers and probes for the detection of Shiga toxin genes, including novel subtypes. Int J Food Microbiol 2024; 419:110744. [PMID: 38763050 DOI: 10.1016/j.ijfoodmicro.2024.110744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 05/03/2024] [Accepted: 05/10/2024] [Indexed: 05/21/2024]
Abstract
Shiga toxin-producing Escherichia coli (STEC) are foodborne enteric pathogens. STEC are differentiated from other E. coli by detection of Shiga toxin (Stx) or its gene (stx). The established nomenclature of Stx identifies ten subtypes (Stx1a, Stx1c, Stxd, Stx2a to Stx2g). An additional nine subtypes have been reported and described (Stx1e, Stx2h to Stx2o). Many PCR protocols only detect a subset of Stx subtypes which limits their inclusivity. Here we describe a real-time PCR assay inclusive of the DNA sequences of representatives of all currently described Stx subtypes. A multiplex real-time PCR assay for detection of stx was developed using nine primers and four probes. Since the identification of STEC does not require differentiation of stx subtypes, the probes use the same fluorescent reporter to enable detection of multiple possible targets in a single reaction. The PCR mixture includes an internal positive control to detect inhibition of the reaction. Thus, the protocol can be performed on a two-channel real-time PCR platform. To reduce the biosafety risk inherent in the use of STEC cultures as process controls, the protocol also includes the option of a non-pathogenic E. coli transformant carrying a plasmid encoding the targeted fragment of the stx2a sequence. The inclusivity of the PCR was assessed against colonies of 137 STEC strains and one strain of Shigella dysenteriae, including strains carrying single copies of stx representing fourteen subtypes (stx1 a, c, d; stx2 a-j and o). Five additional subtypes (stx1e, 2k, 2l, 2m and 2n) were represented by E. coli transformed with plasmids encoding toxoid (enzymatically inactive A subunit) sequences. The exclusivity panel consisted of 70 bacteria, including 21 stx-negative E. coli. Suitability for food analysis was assessed with artificially inoculated ground beef, spinach, cheese, and apple cider. The real-time PCR generated positive results for all 19 stx subtypes, represented by colonies of STEC, S. dysenteriae and E. coli transformants carrying stx toxoid plasmids. Tests of exclusivity panel colonies were all negative. The real-time PCR detected the presence of stx in all inoculated food enrichments tested, and the presence of STEC was confirmed by isolation.
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Affiliation(s)
- Tanis McMahon
- Health Canada/Santé Canada, Bureau of Microbial Hazards, Ottawa, Ontario, Canada
| | - Sarah Clarke
- Health Canada/Santé Canada, Bureau of Microbial Hazards, Ottawa, Ontario, Canada
| | - Mylène Deschênes
- Canadian Food Inspection Agency/Agence canadienne d'inspection des aliments, Ottawa Laboratory Carling, Ottawa, Ontario, Canada
| | - Kyle Tapp
- Canadian Food Inspection Agency/Agence canadienne d'inspection des aliments, Ottawa Laboratory Carling, Ottawa, Ontario, Canada
| | - Burton Blais
- Canadian Food Inspection Agency/Agence canadienne d'inspection des aliments, Ottawa Laboratory Carling, Ottawa, Ontario, Canada
| | - Alexander Gill
- Health Canada/Santé Canada, Bureau of Microbial Hazards, Ottawa, Ontario, Canada.
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McMAHON T, Bastian J, Alshawa I, Gill A. PCR Primers for Screening Food for Verotoxin-Producing Escherichia coli, Inclusive of Three vt1 and Seven vt2 Subtypes. J Food Prot 2021; 84:296-302. [PMID: 32977337 DOI: 10.4315/jfp-20-233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 09/21/2020] [Indexed: 11/11/2022]
Abstract
ABSTRACT Verotoxin-producing Escherichia coli (VTEC; also known as Shiga toxin-producing E. coli) is a significant cause of foodborne illnesses around the world. Due to the serological and genomic diversity of VTEC, methods of detection for VTEC in food samples require detection of verotoxin or its gene vt (also known as stx). The current taxonomy of vt identifies three vt1 (a, c, d) and seven vt2 (a to g) subtypes. PCR detection of vt is convenient and rapid, but protocols may not detect all currently identified variants or subtypes of vt. The Health Canada Compendium of Analytical Methods protocol for the analysis of food for VTEC is MFLP-52. MFLP-52 includes a VT Screening PCR that is used to determine the presumptive presence of VTEC by the detection of vt in food enrichments and to differentiate VTEC from other isolates. The VT Screening PCR was developed prior to the establishment of the current vt taxonomy. An evaluation of VT Screening PCR for detection of the 10 established vt subtypes was performed, and it was discovered that the method could not detect subtypes vt1d and vt2f. Additional primers and a modified protocol were developed, and the modified VT Screening PCR was tested against an inclusivity panel of 50 VTEC strains, including representatives of 10 vt subtypes, and an exclusivity panel of 30 vt-negative E. coli from various sources, to ensure specificity. The reliability of MFLP-52 with the modified VT Screening PCR was assessed by analysis of four priority food matrices (ground beef, lettuce, cheese, and apple cider) inoculated with a VTEC strain at 2 to 5 CFU/25 g. The modified VT Screening PCR was determined to be able to detect all 10 vt subtypes and reliably detect the presence of VTEC in all tested food enrichments. HIGHLIGHTS
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Affiliation(s)
- Tanis McMAHON
- Health Canada, Bureau of Microbial Hazards, 251 Sir Frederick Banting Driveway, Ottawa, Ontario, Canada K1A 0K9
| | - Jillian Bastian
- Health Canada, Bureau of Microbial Hazards, 251 Sir Frederick Banting Driveway, Ottawa, Ontario, Canada K1A 0K9
| | - Inas Alshawa
- Health Canada, Bureau of Microbial Hazards, 251 Sir Frederick Banting Driveway, Ottawa, Ontario, Canada K1A 0K9
| | - Alexander Gill
- Health Canada, Bureau of Microbial Hazards, 251 Sir Frederick Banting Driveway, Ottawa, Ontario, Canada K1A 0K9.,(ORCID: https://orcid.org/0000-0003-2380-2148 [A.G.])
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Tarr GAM, Lin CY, Vandermeer B, Lorenzetti DL, Tarr PI, Chui L, Hartling L, Freedman SB. Diagnostic Test Accuracy of Commercial Tests for Detection of Shiga Toxin-Producing Escherichia coli: A Systematic Review and Meta-Analysis. Clin Chem 2020; 66:302-315. [PMID: 32040589 DOI: 10.1093/clinchem/hvz006] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 08/07/2019] [Indexed: 12/25/2022]
Abstract
BACKGROUND Rapid detection of Shiga toxin-producing Escherichia coli (STEC) enables appropriate monitoring and treatment. We synthesized available evidence to compare the performance of enzyme immunoassay (EIA) and PCR tests for the detection of STEC. METHODS We searched published and gray literature for studies of STEC EIA and/or PCR diagnostic test accuracy relative to reference standards including at least one nucleic acid amplification test. Two reviewers independently screened studies, extracted data, and assessed quality with the second version of the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. Bivariate random effects models were used to meta-analyze the clinical sensitivity and specificity of commercial EIA and PCR STEC diagnostic tests, and summary receiver operator characteristic curves were constructed. We evaluated the certainty of evidence with the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. RESULTS We identified 43 articles reflecting 25 260 specimens. Meta-analysis of EIA and PCR accuracy included 25 and 22 articles, respectively. STEC EIA pooled sensitivity and specificity were 0.681 (95% CI, 0.571-0.773; very low certainty of evidence) and 1.00 (95% CI, 0.998-1.00; moderate certainty of evidence), respectively. STEC PCR pooled sensitivity and specificity were 1.00 (95% CI, 0.904-1.00; low certainty of evidence) and 0.999 (95% CI, 0.997-0.999; low certainty of evidence), respectively. Certainty of evidence was downgraded because of high risk of bias. CONCLUSIONS PCR tests to identify the presence of STEC are more sensitive than EIA tests, with no meaningful loss of specificity. However, given the low certainty of evidence, our results may overestimate the difference in performance.
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Affiliation(s)
- Gillian A M Tarr
- Department of Pediatrics, University of Calgary, Calgary, AB, Canada
| | - Chu Yang Lin
- Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Ben Vandermeer
- Department of Pediatrics, University of Alberta, Edmonton, AB, Canada
| | | | - Phillip I Tarr
- Department of Pediatrics, Washington University in St. Louis School of Medicine, St. Louis, MO
| | - Linda Chui
- Department of Laboratory Medicine and Pathology, University of Alberta and Alberta Precision Laboratories-ProvLab, Edmonton, AB, Canada
| | - Lisa Hartling
- Department of Pediatrics, University of Alberta, Edmonton, AB, Canada
| | - Stephen B Freedman
- Sections of Pediatric Emergency Medicine and Gastroenterology, Department of Pediatrics, Alberta Children's Hospital and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
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Development and Evaluation of a Novel VHH-Based Immunocapture Assay for High-Sensitivity Detection of Shiga Toxin Type 2 (Stx2) in Stool Samples. J Clin Microbiol 2020; 58:JCM.01566-19. [PMID: 31826960 DOI: 10.1128/jcm.01566-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 12/04/2019] [Indexed: 12/16/2022] Open
Abstract
Shiga toxin (Stx)-producing Escherichia coli (STEC) is the main cause of postdiarrheal hemolytic-uremic syndrome (HUS), a life-threatening clinical complication characterized by hemolytic anemia, thrombocytopenia, and acute renal failure that mainly affects children. A relevant feature of STEC strains is the production of Stx, and all of them express Stx1 and/or Stx2 regardless of the strain serotype. Therefore, Stx detection assays are considered the most suitable methods for the early detection of STEC infections. Single-domain antibodies from camelids (VHHs) exhibit several advantages in comparison with conventional antibodies, making them promising tools for diagnosis. In this work, we have exploited VHH technology for the development of an immunocapture assay for Stx2 detection. Thirteen anti-Stx2 VHHs previously obtained from a variable-domain repertoire library were selected and evaluated in 130 capture-detection pair combinations for Stx detection. Based on this analysis, two VHHs were selected and a double VHH-based biotin-streptavidin capture enzyme-linked immunosorbent assay (ELISA) with spectrophotometric detection was developed and optimized for Stx2 detection. This assay showed an excellent analytical and clinical sensitivity in both STEC culture supernatants and stool samples even higher than the sensitivity of a commercial ELISA. Furthermore, based on the analysis of stool samples, the VHH-based ELISA showed high correlation with stx 2 detection by PCR and a commercial rapid membrane-based immunoassay. The intrinsic properties of VHHs (high target affinity and specificity, stability, and ease of expression at high yields in recombinant bacteria) and their optimal performance for Stx detection make them attractive tools for the diagnosis of HUS related to STEC (STEC-HUS).
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Fagerquist CK, Zaragoza WJ, Carter MQ. Top-Down Proteomic Identification of Shiga Toxin 1 and 2 from Pathogenic Escherichia coli Using MALDI-TOF-TOF Tandem Mass Spectrometry. Microorganisms 2019; 7:E488. [PMID: 31731469 PMCID: PMC6920754 DOI: 10.3390/microorganisms7110488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2019] [Revised: 10/17/2019] [Accepted: 10/23/2019] [Indexed: 12/14/2022] Open
Abstract
Shiga-toxin-producing Escherichia coli (STEC) are a burden on agriculture and a threat to public health. Rapid methods are needed to identify STEC strains and characterize the Shiga toxin (Stx) they produce. We analyzed three STEC strains for Stx expression, using antibiotic induction, matrix-assisted laser desorption/ionization time-of-flight-time-of-flight (MALDI-TOF-TOF) mass spectrometry, and top-down proteomic analysis. E. coli O157:H- strain 493/89 is a clinical isolate linked to an outbreak of hemolytic uremic syndrome (HUS) in Germany in the late 1980s. E. coli O145:H28 strains RM12367-C1 and RM14496-C1 were isolated from an agricultural region in California. The stx operon of the two environmental strains were determined by whole genome sequencing (WGS). STEC strain 493/89 expressed Shiga toxin 2a (Stx2a) as identified by tandem mass spectrometry (MS/MS) of its B-subunit that allowed identification of the type and subtype of the toxin. RM12367-C1 also expressed Stx2a as identified by its B-subunit. RM14496-C1 expressed Shiga toxin 1a (Stx1a) as identified from its B-subunit. The B-subunits of Stx1 and Stx2 both have an intramolecular disulfide bond. MS/MS was obtained on both the disulfide-bond-intact and disulfide-bond-reduced B-subunit, with the latter being used for top-down proteomic identification. Top-down proteomic analysis was consistent with WGS.
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Affiliation(s)
- Clifton K. Fagerquist
- Produce Safety & Microbiology, Agricultural Research Service, U.S. Department of Agriculture, 800 Buchanan Street, Albany, CA 94710, USA; (W.J.Z.); (M.Q.C.)
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Rapid culture-based identification of Shiga toxin-producing Escherichia coli and Shigella spp./Enteroinvasive E. coli using the eazyplex® EHEC complete assay. Eur J Clin Microbiol Infect Dis 2019; 39:151-158. [PMID: 31529306 DOI: 10.1007/s10096-019-03704-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 09/04/2019] [Indexed: 12/14/2022]
Abstract
Shiga toxin-producing Escherichia coli (STEC) and Shigella spp./enteroinvasive E. coli (EIEC) are common diarrheagenic bacteria that cause sporadic diseases and outbreaks. Clinical manifestations vary from mild symptoms to severe complications. For microbiological diagnosis, culture confirmation of a positive stool screening PCR test is challenging because of time-consuming methods for isolation of strains, wide variety of STEC pathotypes, and increased emergence of non-classical strains with unusual serotypes. Therefore, molecular assays for the rapid identification of suspect colonies growing on selective media are very useful. In this study, the performance of the newly introduced eazyplex® EHEC assay based on loop-mediated isothermal amplification (LAMP) was evaluated using 18 representative STEC and Shigella strains and 31 isolates or positive-enrichment broths that were collected from clinical stool samples following screening by BD MAX™ EBP PCR. Results were compared to real-time PCR as a reference standard. Overall, sensitivities and specificities of the eazyplex® EHEC were as follows: 94.7% and 100% for Shiga toxin 1 (stx1), 100% and 100% for stx2, 93.3% and 97.1% for intimin (eae), 100% and 100% for enterohemolysin A (ehlyA), and 100% and 100% for invasion-associated plasmid antigen H (ipaH) as Shigella spp./EIEC target, respectively. Sample preparation for LAMP took only some minutes, and the time to result of the assay ranged from 8.5 to 13 min. This study shows that eazyplex® EHEC is a very fast and easy to perform molecular assay that provides reliable results as a culture confirmation assay for the diagnosis of STEC and Shigella spp./EIEC infections.
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Sánchez S, Llorente MT, Ramiro R, Herrera-León L, Herrera-León S. Evaluation of the SHIGA TOXIN QUIK CHEK after overnight enrichment as screening tool for Shiga toxin-producing Escherichia coli detection in human fecal samples. Diagn Microbiol Infect Dis 2019; 94:218-222. [PMID: 30885395 DOI: 10.1016/j.diagmicrobio.2019.01.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 01/17/2019] [Accepted: 01/20/2019] [Indexed: 12/18/2022]
Abstract
We evaluated the SHIGA TOXIN QUIK CHEK (STQC) on its suitability for Shiga toxin-producing Escherichia coli (STEC) testing on human fecal samples after overnight enrichment. Our in-house PCR-based protocol for STEC detection was used as the standard for comparison. STQC detected all described Shiga toxin subtypes with the only exception of Stx2f. In comparison to PCR, STQC performed with an overall sensitivity of 55.4%, specificity of 100.0%, positive predictive value of 100.0%, negative predictive value of 73.0%, infinite positive likelihood ratio, and negative likelihood ratio of 0.45. We conclude that STQC may not be considered a suitable screening tool for STEC detection in human fecal samples, although it could be useful for laboratories where PCR is not a routine tool for STEC screening yet, subject to the confirmation of negative samples by a reference laboratory with full diagnostic capabilities.
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Affiliation(s)
- Sergio Sánchez
- Reference and Research Laboratory of Food and Waterborne Bacterial Infections, National Center for Microbiology, Institute of Health Carlos III, Majadahonda, Madrid, Spain.
| | - María Teresa Llorente
- Reference and Research Laboratory of Food and Waterborne Bacterial Infections, National Center for Microbiology, Institute of Health Carlos III, Majadahonda, Madrid, Spain
| | - Raquel Ramiro
- Reference and Research Laboratory of Food and Waterborne Bacterial Infections, National Center for Microbiology, Institute of Health Carlos III, Majadahonda, Madrid, Spain
| | - Laura Herrera-León
- Reference and Research Laboratory of Food and Waterborne Bacterial Infections, National Center for Microbiology, Institute of Health Carlos III, Majadahonda, Madrid, Spain
| | - Silvia Herrera-León
- Reference and Research Laboratory of Food and Waterborne Bacterial Infections, National Center for Microbiology, Institute of Health Carlos III, Majadahonda, Madrid, Spain
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Clinically-relevant Shiga toxin 2 subtypes from environmental Shiga toxin-producing Escherichia coli identified by top-down/middle-down proteomics and DNA sequencing. CLINICAL MASS SPECTROMETRY 2018; 11:27-36. [PMID: 34841070 DOI: 10.1016/j.clinms.2018.12.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 11/30/2018] [Accepted: 12/02/2018] [Indexed: 12/12/2022]
Abstract
Thirty-five environmental isolates of Shiga toxin-producing Escherichia coli (STEC) were analyzed by MALDI-TOF-TOF mass spectrometry, top-down/middle-down proteomics and DNA sequencing. Clinically-relevant Shiga toxin 2 (Stx2) produced by these STEC strains were subtyped based on MS and MS/MS (tandem mass spectrometry) of the intact B-subunit (top-down) and A2 fragment (middle-down) of the A-subunit using antibiotic-induced protein expression. Antibiotic induction of Stx2 was found to be strain dependent. By proteomic analysis, seventeen strains were identified as Stx2a, six strains as Stx2c, four strains as either Stx2a or 2c and eight strains as either Stx2a, 2c or 2d. DNA sequencing indicated only stx 2a and stx 2c genes as being present in these strains. Weak induction of Stx2 for certain strains made it difficult to distinguish between clinical subtypes by proteomic analysis. Very weak toxin induction in eight strains was consistent with a ∼1300 bp transposon insertion in the stx 2c A-subunit gene identified by DNA sequencing. DNA sequencing also revealed the presence of two bacteriophage (BP) in three strains with a stx 2a gene in each BP genome. Middle-down proteomic analysis of the A2 fragment confirmed expression of two stx 2a genes present in one of these strains based on a slight difference in the amino acid sequence (D ↔ E substitution) in the two A2 fragments.
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Key Words
- BP, bacteriophage
- ELISA, enzyme-linked immunoassay
- GB, gas phase basicity
- Gb3, globotriaosylceramide
- MALDI-TOF-TOF, matrix-assisted laser desorption/ionization time-of-flight-time-of-flight
- MS, mass spectrometry
- MS/MS, tandem mass spectrometry
- PCR, polymerase chain reaction
- STEC, Shiga toxin-producing Escherichia coli
- Stx, Shiga toxin
- Stx1, Shiga toxin 1
- Stx2, Shiga toxin 2
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Direct-from-Stool Testing for Shiga Toxins by an Immunochromatographic Assay Is Insensitive for Detection of Shigatoxigenic Escherichia coli. J Clin Microbiol 2018; 56:JCM.01209-18. [PMID: 30282784 DOI: 10.1128/jcm.01209-18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Twenty-seven years of screening for Shiga toxin-producing Escherichia coli in a university hospital. Brussels, Belgium, 1987-2014. PLoS One 2018; 13:e0199968. [PMID: 29965972 PMCID: PMC6028080 DOI: 10.1371/journal.pone.0199968] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 06/17/2018] [Indexed: 11/19/2022] Open
Abstract
Objective Since 1987 all fecal samples referred to the clinical microbiology laboratory of the UZ Brussel were screened for the presence of Shiga toxin-producing E. coli (STEC). In this study all STEC strains isolated over a period of 27 years (1987–2014) were reexamined to achieve deeper insight in the STEC infections in our patient population. Methods A total of 606 STEC strains from 604 patients were subjected to molecular methods for shiga toxin (stx) subtyping, detection of additional virulence genes, typing of the O-serogroups, and phylogenetic relatedness assessment of STEC O157:H7/H-. Results Since the introduction of PCR in 1991 the annual positivity rates varied between 1.1% and 2.7%. The isolation rate of STEC O157:H7/H- remained stable over the years while the isolation rate of non-O157 serotypes increased, mainly since 2011. The majority of the patients were children. Uncomplicated- and bloody diarrhea were the most prevalent gastrointestinal manifestations (respectively 51.9% and 13.6%), 4.3% of the strains were related to the hemolytic uremic syndrome (HUS), and 30.2% of the patients showed none of these symptoms. The strains were very diverse; they belonged to 72 different O-serovars and all stx subtypes except stx1d and stx2g were identified. Out of the 23 stx2f-positives one was associated with HUS and one belonged to the E. albertii species. As seen in other studies, the frequency of strains of the O157:H7/H- serotype and strains carrying stx2a, eaeA and ehxA was higher in patients with HUS. Conclusions The characteristics and trends of STEC infection seen in our patient population are similar to those noted in other countries. STEC infections in our hospital are mainly sporadic, and a substantial portion of the patients were asymptomatic carriers. Human STEC Stx2f infection was less rare than previously assumed and we report the first Belgian STEC stx2f HUS case and stx2f positive E. albertii infection.
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Freedman SB, Grisaru S, Xie J, Samuel S, Dixon A, Plint AC, Schnadower D. Management of Shiga toxin producing Escherichia coli-infected children: A multi-national, multi-specialty survey. J Paediatr Child Health 2018; 54:390-397. [PMID: 29111613 DOI: 10.1111/jpc.13778] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 09/03/2017] [Indexed: 12/19/2022]
Abstract
AIM Research has highlighted the potential role that hydration status may play in predicting outcomes in Shiga toxin-producing Escherichia coli (STEC)-infected children. Because little is known about the management of STEC-infected children in the pre-haemolytic uremic syndrome phase, we compared paediatric emergency medicine and nephrologist-stated management approaches to STEC-infected children. METHODS Members of the Pediatric Emergency Research Canada (PERC; n = 228), the Pediatric Emergency Medicine Collaborative Research Committee (PEM CRC; n = 221) and the Canadian Association of Pediatric Nephrologists (CAPN; n = 66) were surveyed. Five individualised e-mail requests containing a link to a 42-question web-based survey were sent to eligible participants. RESULTS Of 496 potentially eligible participants, 276 (56%) submitted complete survey responses. In children with classic features of STEC infection, baseline haemoglobin/haematocrit is obtained by 54% of PERC, 41% of PEM CRC and 83% of CAPN members (P < 0.001), and baseline renal function is obtained by 51% of PERC, 38% of PEM CRC and 83% of CAPN members (P < 0.001). Intravenous fluids are more often recommended by nephrologists (28%) compared with PEM physicians (7%), P < 0.001. In children with known E. coli O157:H7 infection, nephrologists more commonly recommend clinical follow-up (P = 0.003), complete blood counts (P < 0.001) and renal function/electrolyte testing (P < 0.001). Intravenous fluid administration and admission are more commonly recommended by nephrologists (P = 0.03 and P < 0.001, respectively). CONCLUSION Compared with paediatric nephrologists, paediatric emergency medicine physicians are less likely to perform baseline and follow-up blood tests and to administer intravascular volume expansion in children at risk of, and with confirmed, E. coli O157:H7 infection.
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Affiliation(s)
- Stephen B Freedman
- Section of Pediatric Emergency Medicine and Gastroenterology, Alberta Children's Hospital, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Silviu Grisaru
- Section of Pediatric Nephrology, Alberta Children's Hospital, Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Jianling Xie
- Section of Pediatric Emergency Medicine, Alberta Children's Hospital, University of Calgary, Calgary, Alberta, Canada
| | - Susan Samuel
- Section of Pediatric Nephrology, Alberta Children's Hospital, Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Andrew Dixon
- Division of Pediatric Emergency Medicine, Stollery Children's Hospital, Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Amy C Plint
- Division of Pediatric Emergency Medicine, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, Ontario, Canada
| | - David Schnadower
- Division of Pediatric Emergency Medicine, Washington University School of Medicine, St. Louis, Missouri, United States
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Clinical Evaluation and Cost Analysis of Great Basin Shiga Toxin Direct Molecular Assay for Detection of Shiga Toxin-Producing Escherichia coli in Diarrheal Stool Specimens. J Clin Microbiol 2016; 55:519-525. [PMID: 27927919 DOI: 10.1128/jcm.01939-16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 11/24/2016] [Indexed: 12/17/2022] Open
Abstract
The Shiga Toxin Direct molecular assay (ST Direct) relies on nucleic acid amplification and solid array-based amplicon detection to identify Shiga toxin-producing Escherichia coli (STEC) in preserved stool specimens. Genes encoding Shiga toxin (stx1 and stx2), as well as the E. coli serotype O:157-specific marker rfbE, are simultaneously detected within 2 h. ST Direct was evaluated using 1,084 prospectively collected preserved stool specimens across five clinical centers. An additional 55 retrospectively collected, frozen specimens were included to increase the number of positive specimens evaluated. Results were compared to results from routine culture and an enzyme immunoassay (EIA) specific for the recovery and identification of STEC. ST Direct was found to be 93.2% sensitive and 99.3% specific for detection of stx1 and stx2 and 95.7% sensitive and 99.3% specific for detection of E. coli serotype O:157. All specimens with false-positive results were found to contain stx1 or stx2 or were found to be positive for serotype O:157 when analyzed using alternative molecular methods. All 4 false-negative stx1 or stx2 results were reported for frozen, retrospectively tested specimens. In all cases, the specimens tested positive for stx by an alternative FDA-cleared nucleic acid amplification test (NAAT) but were negative for stx1 and stx2 following nucleic acid sequence analysis. Based on these data, culture and EIA-based methods for detection of STEC are only 33% sensitive compared to molecular tests. A retrospective cost analysis demonstrated 59% of the cost of routine stool culture to be attributable to the identification of STEC. Taken together, these data suggest that ST Direct may provide a cost-effective, rapid molecular alternative to routine culture for the identification of STEC in preserved stool specimens.
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