VTEC O157 subtypes associated with the most severe clinical symptoms in humans constitute a minor part of VTEC O157 isolates from Danish Cattle

Roldgaard, Bent; Scheutz, Flemming; Boel, Jeppe; Aabo, Søren; Schultz, Anna Charlotte; Cheasty, T.; Nielsen, Eva Møller; Olsen, Katharina E. P.; Christensen, Bjarke Bak

doi:10.1016/j.ijmm.2004.05.001

Cited by 20 publications

(24 citation statements)

References 17 publications

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“…Although Stx 2c has been reported to have the same level of toxicity as Stx 2 in mice (32), the risk of developing HUS after infection with stx 2c -containing STEC has been reported to be significantly lower than with STEC possessing the stx 2 toxin genotype (14). This is also in agreement with other studies that report that most HUS cases were associated with E. coli strains carrying stx 2 rather than other stx 2 variant genes (6,49).…”

Section: Resultssupporting

confidence: 85%

Genotypic Characterization and Prevalence of Virulence Factors among Canadian Escherichia coli O157:H7 Strains

Ziebell

Steele

Zhang

et al. 2008

Appl Environ Microbiol

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In this study, the association between genotypic and selected phenotypic characteristics was examined in a collection of Canadian Escherichia coli O157:H7 strains isolated from humans and cattle in the provinces of Alberta, Ontario, Saskatchewan, and Quebec. In a subset of 69 strains selected on the basis of specific phage types (PTs), a strong correlation between the lineage-specific polymorphism assay (LSPA6) genotype and PT was observed with all strains of PTs 4, 14, 21, 31, 33, and 87 belonging to the LSPA6 lineage I (LSPA6-LI) genotype, while those of PTs 23, 45, 67, and 74 belonged to LSPA6 lineage II (LSPA6-LII) genotypes. This correlation was maintained when additional strains of each PT were tested. E. coli O157:H7 strains with the LSPA6-LI genotype were much more common in the collection than were the LSPA6-LII or lineage I/II (LSPA6-LI/II)-related genotypes (82.6, 11.2, and 5.8%, respectively). Of the strains tested, proportionately more LSPA6-LI than LSPA6-LII genotype strains were isolated from humans (52.7% versus 19.7%) than from cattle (47.8% versus 80.2%). In addition, 96.7% of the LSPA6-LII strains carried the stx 2c variant gene, while only 50.0% of LSPA6-LI/II and 2.7% of LSPA6-LI strains carried this gene. LSPA6-LII strains were also significantly more likely to possess the colicin D gene, cda (50.8% versus 23.2%), and have combined resistance to streptomycin, sulfisoxazole, and tetracycline (72.1% versus 0.9%) than were LSPA6-LI strains. The LSPA6 genotype-and PT-related characteristics identified may be important markers of specific ecotypes of E. coli O157:H7 that have unique epidemiological and virulence characteristics.Shiga toxin (Stx)-producing Escherichia coli (STEC) O157:H7 is the leading cause of hemorrhagic colitis and hemolytic-uremic syndrome (HUS) throughout the world (16,23,25). Cattle colonized by E. coli O157:H7 are thought to be the primary reservoir of this bacterium, and its transmission to humans frequently results from the ingestion of contaminated food and water (16,23,35).Results of multiple studies suggest that E. coli O157:H7 strains may differ in their association with human disease. An increasing body of evidence has shown that strains can differ in the type and level of expression of virulence factors (3,28,29,47,48). Similarly, in vivo testing of strains in the gnotobiotic pig model has shown that human isolates caused more severe symptoms than cattle isolates, suggesting that cattle-derived strains may differ in their virulence with respect to those isolated from humans (3). High-resolution genotyping studies on E. coli O157:H7 strains from the United States and Australia using octamer-based genome scanning (OBGS) first demonstrated that the E. coli O157:H7 clonal complex has diverged through two primary lineages, designated lineage I and lineage II, and that these two lineages differ in their frequency of association with human disease (28,29,54). Subsequent studies using a more efficient multiplex PCR assay based on OBGS, the lineage specific polymorphism ass...

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Section: Resultssupporting

confidence: 85%

Genotypic Characterization and Prevalence of Virulence Factors among Canadian Escherichia coli O157:H7 Strains

Ziebell

Steele

Zhang

et al. 2008

Appl Environ Microbiol

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“…EHEC strains are rapidly evolving through the integration of laterally acquired virulence genes (62,84) and vary in their ability to adhere to epithelial cells, cause disease in humans, colonize animals, and survive in the environment (1,21,68,93). Differential regulation of the LEE among EHEC strains 86-24, EDL933, and Sakai has been observed in studies examining the roles of RpoS and GrlA in EHEC virulence (18,37,38,49,80,86).…”

Section: Discussionmentioning

confidence: 99%

Hfq Virulence Regulation in Enterohemorrhagic Escherichia coli O157:H7 Strain 86-24

et al. 2011

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Enterohemorrhagic Escherichia coli O157:H7 (EHEC) causes bloody diarrhea and hemolytic-uremic syndrome. EHEC encodes the sRNA chaperone Hfq, which is important in posttranscriptional regulation. In EHEC strain EDL933, Hfq acts as a negative regulator of the locus of enterocyte effacement (LEE), which encodes most of the proteins involved in type III secretion and attaching and effacing (AE) lesions. Here, we deleted hfq in the EHEC strain 86-24 and compared global transcription profiles of the hfq mutant and wild-type (WT) strains in exponential growth phase. Deletion of hfq affected transcription of genes common to nonpathogenic and pathogenic strains of E. coli as well as pathogen-specific genes. Downregulated genes in the hfq mutant included ler, the transcriptional activator of all the LEE genes, as well as genes encoded in the LEE2 to -5 operons. Decreased expression of the LEE genes in the hfq mutant occurred at middle, late, and stationary growth phases. We also confirmed decreased regulation of the LEE genes by examining the proteins secreted and AE lesion formation by the hfq mutant and WT strains. Deletion of hfq also caused decreased expression of the two-component system qseBC, which is involved in interkingdom signaling and virulence gene regulation in EHEC, as well as an increase in expression of stx 2AB , which encodes the deadly Shiga toxin. Altogether, these data indicate that Hfq plays a regulatory role in EHEC 86-24 that is different from what has been reported for EHEC strain EDL933 and that the role of Hfq in EHEC virulence regulation extends beyond the LEE.Enterohemorrhagic Escherichia coli O157:H7 (EHEC) is a food-borne pathogen that causes severe bloody diarrhea and is often associated with complications, including hemolytic-uremic syndrome (HUS), seizures, cerebral edema, and/or coma (42). EHEC attaches intimately to intestinal epithelial cells and triggers extensive cytoskeletal rearrangements, resulting in attaching and effacing (AE) lesions and formation of a characteristic pedestal structure (40,41,46). Most of the genes involved in AE lesion formation are carried within a chromosomal pathogenicity island called the locus of enterocyte effacement (LEE) (53). The LEE contains five major operons (LEE1 to -5) that encode a type III secretion (TTS) system and effector proteins. EHEC's arsenal of virulence factors also includes non-LEE-encoded effector proteins that increase adherence or mediate colonization of host epithelial cells (8,16,26,27,32,84,87,88).The mortality associated with EHEC infections is due to the production and release of a Shiga toxin (Stx) by these bacteria. EHEC expresses Stx, and this potent inhibitor of protein synthesis can be absorbed systemically, where it binds to receptors found in the kidneys and the central nervous system, thus causing the complications associated with EHEC disease (42).Regulation of EHEC virulence genes is extremely complex and involves interkingdom signaling (12). EHEC senses the host-derived signals epinephrine and norepinephrine as well...

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“…The prevalence of these BISG types in New Zealand cattle is unknown. Also, since certain O157 phage types have been found more frequently in animals than in humans (40,55), further evaluation of P-BIT clustering with O157 phage typing could reveal that cluster 3 and the nonhuman cluster 1 correspond to particular O157 phage types associated with animals.…”

Section: Discussionmentioning

confidence: 99%

Molecular Risk Assessment and Epidemiological Typing of Shiga Toxin-Producing Escherichia coli by Using a Novel PCR Binary Typing System

Brandt

King

Cornelius

et al. 2011

Appl Environ Microbiol

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Shiga toxin-producing Escherichia coli (STEC) is a zoonotic pathogen that causes diarrheal disease in humans and is of public health concern because of its ability to cause outbreaks and severe disease such as hemorrhagic colitis or hemolytic-uremic syndrome. More than 400 serotypes of STEC have been implicated in outbreaks and sporadic human disease. The aim of this study was to develop a PCR binary typing (P-BIT) system that could be used to aid in risk assessment and epidemiological studies of STEC by using gene targets that would represent a broad range of STEC virulence genes. We investigated the distribution of 41 gene targets in 75 O157 and non-O157 STEC isolates and found that P-BIT provided 100% typeability for isolates, gave a diversity index of 97.33% (compared with 99.28% for XbaI pulsed-field gel electrophoresis [PFGE] typing), and produced 100% discrimination for non-O157 STEC isolates. We identified 24 gene targets that conferred the same level of discrimination and produced the same cluster dendrogram as the 41 gene targets initially examined. P-BIT clustering identified O157 from non-O157 isolates and identified seropathotypes associated with outbreaks and severe disease. Numerical analysis of the P-BIT data identified several genes associated with human or nonhuman sources as well as high-risk seropathotypes. We conclude that P-BIT is a useful approach for subtyping, offering the advantage of speed, low cost, and potential for strain risk assessment that can be used in tandem with current molecular typing schema for STEC.

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VTEC O157 subtypes associated with the most severe clinical symptoms in humans constitute a minor part of VTEC O157 isolates from Danish Cattle

Cited by 20 publications

References 17 publications

Genotypic Characterization and Prevalence of Virulence Factors among Canadian Escherichia coli O157:H7 Strains

Genotypic Characterization and Prevalence of Virulence Factors among Canadian Escherichia coli O157:H7 Strains

Hfq Virulence Regulation in Enterohemorrhagic Escherichia coli O157:H7 Strain 86-24

Molecular Risk Assessment and Epidemiological Typing of Shiga Toxin-Producing Escherichia coli by Using a Novel PCR Binary Typing System

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