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Comparative analysis of super-shedder strains of Escherichia coli O157:H7 reveals distinctive genomic features and a strongly aggregative adherent phenotype on bovine rectoanal junction squamous epithelial cells.

Cote R, Katani R, Moreau MR, Kudva IT, Arthur TM, DebRoy C, Mwangi MM, Albert I, Raygoza Garay JA, Li L, Brandl MT, Carter MQ, Kapur V - PLoS ONE (2015)

Bottom Line: A large number of non-synonymous SNPs and other polymorphisms were identified in SS17 as compared with other O157 strains (EC4115, EDL933, Sakai, TW14359), including in key adherence- and virulence-related loci.Molecular genetic and functional analyses of defined mutants of SS17 suggested that the strongly adherent aggregative phenotype amongst SS isolates is LEE-independent, and likely results from a novel mechanism.Taken together, our study provides a rational framework for investigating the molecular mechanisms associated with SS, and strong evidence that SS O157 isolates have distinctive features and use a LEE-independent mechanism for hyper-adherence to bovine rectal epithelial cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America; The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America.

ABSTRACT
Shiga toxin-producing Escherichia coli O157:H7 (O157) are significant foodborne pathogens and pose a serious threat to public health worldwide. The major reservoirs of O157 are asymptomatic cattle which harbor the organism in the terminal recto-anal junction (RAJ). Some colonized animals, referred to as "super-shedders" (SS), are known to shed O157 in exceptionally large numbers (>104 CFU/g of feces). Recent studies suggest that SS cattle play a major role in the prevalence and transmission of O157, but little is known about the molecular mechanisms associated with super-shedding. Whole genome sequence analysis of an SS O157 strain (SS17) revealed a genome of 5,523,849 bp chromosome with 5,430 open reading frames and two plasmids, pO157 and pSS17, of 94,645 bp and 37,446 bp, respectively. Comparative analyses showed that SS17 is clustered with spinach-associated O157 outbreak strains, and belongs to the lineage I/II, clade 8, D group, and genotype 1, a subgroup of O157 with predicted hyper-virulence. A large number of non-synonymous SNPs and other polymorphisms were identified in SS17 as compared with other O157 strains (EC4115, EDL933, Sakai, TW14359), including in key adherence- and virulence-related loci. Phenotypic analyses revealed a distinctive and strongly adherent aggregative phenotype of SS17 on bovine RAJ stratified squamous epithelial (RSE) cells that was conserved amongst other SS isolates. Molecular genetic and functional analyses of defined mutants of SS17 suggested that the strongly adherent aggregative phenotype amongst SS isolates is LEE-independent, and likely results from a novel mechanism. Taken together, our study provides a rational framework for investigating the molecular mechanisms associated with SS, and strong evidence that SS O157 isolates have distinctive features and use a LEE-independent mechanism for hyper-adherence to bovine rectal epithelial cells.

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Related in: MedlinePlus

Cladogram of SS17 and O157 outbreak strains.Whole genome analysis shows SS17 clusters with the lineage I/II spinach outbreak isolates (EC4115 and TW14359). This indicates a closer relationship with these strains than with the lineage I outbreak isolates (Sakai and EDL933) and the bovine lineage II isolates.
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pone.0116743.g004: Cladogram of SS17 and O157 outbreak strains.Whole genome analysis shows SS17 clusters with the lineage I/II spinach outbreak isolates (EC4115 and TW14359). This indicates a closer relationship with these strains than with the lineage I outbreak isolates (Sakai and EDL933) and the bovine lineage II isolates.

Mentions: One of the important aspects of this study was to determine genomic level factors that have the potential to contribute to the super-shedder phenotype, specifically genetic loci that can be used to distinguish and define super-shedder isolates. However, it is very difficult to distinguish a non-super-shedder from a super-shedder isolate since fecal shedding levels are temporal and can vary from animal to animal [13]. For instance, the level of shedding usually increases during the warmer months, whereas the colder months see a decrease in shedding. Moreover, a low shedding isolate may be obtained during the same season and even at the same time as a high shedder and still not be considered a non-super-shedder as the peak shedding may not have been reached at the time of sampling. With this in mind, we used the previously sequenced O157 genomes as references that were considered to be distinct from SS17 according to the whole genome clustering (Fig. 4) [27–30]. We performed whole genome comparisons and identified polymorphism unique to SS17, concentrating on those polymorphisms that are in virulence related genes.


Comparative analysis of super-shedder strains of Escherichia coli O157:H7 reveals distinctive genomic features and a strongly aggregative adherent phenotype on bovine rectoanal junction squamous epithelial cells.

Cote R, Katani R, Moreau MR, Kudva IT, Arthur TM, DebRoy C, Mwangi MM, Albert I, Raygoza Garay JA, Li L, Brandl MT, Carter MQ, Kapur V - PLoS ONE (2015)

Cladogram of SS17 and O157 outbreak strains.Whole genome analysis shows SS17 clusters with the lineage I/II spinach outbreak isolates (EC4115 and TW14359). This indicates a closer relationship with these strains than with the lineage I outbreak isolates (Sakai and EDL933) and the bovine lineage II isolates.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4321836&req=5

pone.0116743.g004: Cladogram of SS17 and O157 outbreak strains.Whole genome analysis shows SS17 clusters with the lineage I/II spinach outbreak isolates (EC4115 and TW14359). This indicates a closer relationship with these strains than with the lineage I outbreak isolates (Sakai and EDL933) and the bovine lineage II isolates.
Mentions: One of the important aspects of this study was to determine genomic level factors that have the potential to contribute to the super-shedder phenotype, specifically genetic loci that can be used to distinguish and define super-shedder isolates. However, it is very difficult to distinguish a non-super-shedder from a super-shedder isolate since fecal shedding levels are temporal and can vary from animal to animal [13]. For instance, the level of shedding usually increases during the warmer months, whereas the colder months see a decrease in shedding. Moreover, a low shedding isolate may be obtained during the same season and even at the same time as a high shedder and still not be considered a non-super-shedder as the peak shedding may not have been reached at the time of sampling. With this in mind, we used the previously sequenced O157 genomes as references that were considered to be distinct from SS17 according to the whole genome clustering (Fig. 4) [27–30]. We performed whole genome comparisons and identified polymorphism unique to SS17, concentrating on those polymorphisms that are in virulence related genes.

Bottom Line: A large number of non-synonymous SNPs and other polymorphisms were identified in SS17 as compared with other O157 strains (EC4115, EDL933, Sakai, TW14359), including in key adherence- and virulence-related loci.Molecular genetic and functional analyses of defined mutants of SS17 suggested that the strongly adherent aggregative phenotype amongst SS isolates is LEE-independent, and likely results from a novel mechanism.Taken together, our study provides a rational framework for investigating the molecular mechanisms associated with SS, and strong evidence that SS O157 isolates have distinctive features and use a LEE-independent mechanism for hyper-adherence to bovine rectal epithelial cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America; The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America.

ABSTRACT
Shiga toxin-producing Escherichia coli O157:H7 (O157) are significant foodborne pathogens and pose a serious threat to public health worldwide. The major reservoirs of O157 are asymptomatic cattle which harbor the organism in the terminal recto-anal junction (RAJ). Some colonized animals, referred to as "super-shedders" (SS), are known to shed O157 in exceptionally large numbers (>104 CFU/g of feces). Recent studies suggest that SS cattle play a major role in the prevalence and transmission of O157, but little is known about the molecular mechanisms associated with super-shedding. Whole genome sequence analysis of an SS O157 strain (SS17) revealed a genome of 5,523,849 bp chromosome with 5,430 open reading frames and two plasmids, pO157 and pSS17, of 94,645 bp and 37,446 bp, respectively. Comparative analyses showed that SS17 is clustered with spinach-associated O157 outbreak strains, and belongs to the lineage I/II, clade 8, D group, and genotype 1, a subgroup of O157 with predicted hyper-virulence. A large number of non-synonymous SNPs and other polymorphisms were identified in SS17 as compared with other O157 strains (EC4115, EDL933, Sakai, TW14359), including in key adherence- and virulence-related loci. Phenotypic analyses revealed a distinctive and strongly adherent aggregative phenotype of SS17 on bovine RAJ stratified squamous epithelial (RSE) cells that was conserved amongst other SS isolates. Molecular genetic and functional analyses of defined mutants of SS17 suggested that the strongly adherent aggregative phenotype amongst SS isolates is LEE-independent, and likely results from a novel mechanism. Taken together, our study provides a rational framework for investigating the molecular mechanisms associated with SS, and strong evidence that SS O157 isolates have distinctive features and use a LEE-independent mechanism for hyper-adherence to bovine rectal epithelial cells.

Show MeSH
Related in: MedlinePlus