Comparative analysis of virulence genes, genetic diversity, and phylogeny of Shiga toxin 2g and heat-stable enterotoxin STIa encoding Escherichia coli isolates from humans, animals, and environmental sources

Prager, Rita; Fruth, Angelika; Busch, Ulrich; Tietze, Erhard

doi:10.1016/j.ijmm.2010.06.003

Cited by 59 publications

(68 citation statements)

References 76 publications

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“…STEC/ETEC hybrid strains carrying both stx and est have been isolated from humans and animals (6,(27)(28)(29)(30). Of those, O101:H-isolated from an infant with HUS carried stx2a, estA1, eae, and espP; O2:H27 isolated from a child with diarrhea, an asymptomatic adult, and bovine feces carried stx2a, estA1, and astA (27,28); and O2:H2 isolated from cattle carried stx1a, estA1, and astA (27,29).…”

Section: Discussionmentioning

confidence: 99%

Shiga Toxin Subtypes and Virulence Genes in <i>Escherichia coli</i> Isolated from Cattle

et al. 2017

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SUMMARY: Subtypes of stx1 and stx2 in 45 Shiga toxin-producing Escherichia coli (STEC) strains isolated from cattle were investigated by PCR. Only subtype stx1a was detected among all the stx1-positive strains. The major stx2 subtype was stx2a followed by stx2d, stx2c, stx2b, and stx2g in decreasing order of frequency. stx2c was found in strains of serotypes O157 and O174. stx2d was found in 11 strains. These strains were confirmed by DNA sequencing to carry both the activatable tail and the END motif; all were eae-negative, and 3 contained stx2d as the only stx. stx2g was found in 2 strains in association with stx2a, estA1, and astA. In addition, 7 hybrid strains of shigatoxigenic and enterotoxigenic E. coli (STEC/ETEC) were found to harbor one or both of stx1a and stx2a (stx1a/stx2a ) and estA1. Among 27 serotypes of STEC strains isolated from cattle, O157:H7 and O109:H-strains were eae-positive. Other putative adhesin genes, such as saa, iha, espP, and lpfA O113 were detected in more than 12 serotypes.

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Section: Discussionmentioning

confidence: 99%

Shiga Toxin Subtypes and Virulence Genes in <i>Escherichia coli</i> Isolated from Cattle

et al. 2017

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“…An additional recent report of an E. coli strain isolated from a child with acute diarrhea describes the strain as an enteropathogenic E. coli/ETEC hybrid since the genome contains the locus of enterocyte effacement (LEE) pathogenicity island and a gene encoding LT (11). STEC/ETEC hybrid pathotype strains, carrying a gene expressing Shiga toxin and a gene expressing ST, have been isolated from many sources, including humans, animals, food, and water (4,(12)(13)(14)(15)(16)(17)(18). Some STEC/ETEC hybrid strains have been associated with diarrheal disease and HUS in humans (14,17,19), whereas others have been associated with diarrheal disease in pigs (13,20).…”

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“…Although discrete lineages of ETEC have been identified in high-resolution genomic analysis, ETEC strains are considerably diverse genetically (22,23). Various genome comparison studies using core genome multilocus sequence typing (MLST) (19), MLST based on six genes (7), or pulsed-field gel electrophoresis (16,17) have revealed that hybrid STEC/ETEC genomes are also quite diverse. In addition to strains belonging to the Escherichia coli species, hybrid Shiga toxin-producing Escherichia spp./ETEC strains have been identified that are classified phylogenetically as Escherichia sp.…”

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Hybrid Shiga Toxin-Producing and Enterotoxigenic Escherichia sp. Cryptic Lineage 1 Strain 7v Harbors a Hybrid Plasmid

Leonard

Mammel

Rasko

et al. 2016

Appl Environ Microbiol

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Hybrid isolates of Shiga toxin-producing Escherichia coli (STEC) and enterotoxigenic E. coli (ETEC) encoding heat-stable enterotoxin (ST) are being reported with increasing frequency from a variety of sources. However, information regarding the plasmids that these strains harbor is scarce. In this study, we sequence and characterize a plasmid, p7v, from the STEC/ETEC hybrid strain 7v. Whole-genome phylogenetic analyses of STEC/ETEC hybrid strains and prototype E. coli isolates of other pathotypes placed 7v in the Escherichia sp. cryptic lineage 1 (CL1) clade. The complete plasmid, p7v, was determined to be 229,275 bp and encodes putative virulence factors that are typically carried on STEC plasmids as well as those often carried on ETEC plasmids, indicating that the hybrid nature of the strain extends beyond merely encoding the two toxins. Plasmid p7v carries two copies of sta with identical sequences, which were discovered to be divergent from the sta sequences found in the prototype human ETEC strains. Using a nomenclature scheme based on a phylogeny constructed from sta and stb sequences, the sta encoded on p7v is designated STa4. In silico analysis determined that p7v also encodes the K88 fimbria, a colonization factor usually associated with porcine ETEC plasmids. The p7v sequence and the presence of plasmid-encoded virulence factors are compared to those of other STEC/ETEC CL1 hybrid genomes and reveal gene acquisition/loss at the strain level. In addition, the interrogation of 24 STEC/ETEC hybrid genomes for identification of plasmid replicons, colonization factors, Stx and ST subtypes, and other plasmid-encoded virulence genes highlights the diversity of these hybrid strains. IMPORTANCEHybrid Shiga toxin-producing Escherichia coli/enterotoxigenic Escherichia coli (STEC/ETEC) strains, which have been isolated from environmental, animal, and human clinical samples, may represent an emerging threat as food-borne pathogens. Characterization of these strains is important for assessing virulence potential, aiding in the development of pathogen detection methods, and understanding how the hybrid strains evolve to potentially have a greater impact on public health. This study represents, to our knowledge, both the first characterization of a closed plasmid sequence from a STEC/ETEC hybrid strain and the most comprehensive phylogenetic analysis of available STEC/ETEC hybrid genomes to date. The results demonstrate how the mobility of plasmid-associated virulence genes has resulted in the creation of a diverse plasmid repertoire within the STEC/ ETEC hybrid strains. Pathogenic Escherichia coli strains are categorized into pathotypes or pathovars (pathogenic variants) based on virulenceassociated genes whose expression contributes to particular disease symptoms in the human host (1). The virulence-associated genes that are unique to a pathotype have been used as molecular markers to define the pathotype of a given E. coli isolate. Two E. coli pathotypes that cause a significant burden of illness throughout ...

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“…Similarly, the stx 2f subtype, primarily found in STEC isolated from pigeons (20), has been found in 24 Danish cases with nonsevere disease symptoms (F. Scheutz, unpublished data) and has rarely been implicated in severe human illness (21). Lastly, the stx 2g subtype, originally isolated from STEC in cattle (16), has been isolated from a Danish patient without diarrhea (Scheutz, unpublished) and, more recently, from some human isolates, but in most of these strains, the stx 2g gene was not expressed (19). Since the association of some Stx subtypes with illness remains uncertain, the inability of assays to detect some of these Stx subtypes may not be of significant public health concern.…”

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Specificity of PCR and Serological Assays in the Detection of Escherichia coli Shiga Toxin Subtypes

Feng

Jinneman

Scheutz³

et al. 2011

Appl Environ Microbiol

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Comparative analysis of virulence genes, genetic diversity, and phylogeny of Shiga toxin 2g and heat-stable enterotoxin STIa encoding Escherichia coli isolates from humans, animals, and environmental sources

Cited by 59 publications

References 76 publications

Shiga Toxin Subtypes and Virulence Genes in <i>Escherichia coli</i> Isolated from Cattle

Shiga Toxin Subtypes and Virulence Genes in <i>Escherichia coli</i> Isolated from Cattle

Hybrid Shiga Toxin-Producing and Enterotoxigenic Escherichia sp. Cryptic Lineage 1 Strain 7v Harbors a Hybrid Plasmid

Specificity of PCR and Serological Assays in the Detection of Escherichia coli Shiga Toxin Subtypes

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