Expression of curli by Escherichia coli O157:H7 strains isolated from patients during outbreaks is different from similar strains isolated from leafy green production environments

We previously reported that the strains of Escherichia coli O157:H7 (EcO157) that survived longer in austere soil environment lacked expression of curli, a fitness trait linked with intestinal colonization. In addition, the proportion of curli-positive variants of EcO157 decreased with repeated soil...

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Main Authors: Subbarao Venkata Ravva, Chester Zingapan Sarreal, Michael Bruce Cooley
Format: Article
Language:English
Published: Frontiers Media S.A. 2016-12-01
Series:Frontiers in Cellular and Infection Microbiology
Subjects:
Online Access:http://journal.frontiersin.org/Journal/10.3389/fcimb.2016.00189/full
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spelling doaj-2c9f1bc2c209419faf36e0b7ad7f26e32020-11-24T23:19:37ZengFrontiers Media S.A.Frontiers in Cellular and Infection Microbiology2235-29882016-12-01610.3389/fcimb.2016.00189234763Expression of curli by Escherichia coli O157:H7 strains isolated from patients during outbreaks is different from similar strains isolated from leafy green production environmentsSubbarao Venkata Ravva0Chester Zingapan Sarreal1Michael Bruce Cooley2United States Department of Agriculture, Agricultural Research ServiceUnited States Department of Agriculture, Agricultural Research ServiceUnited States Department of Agriculture, Agricultural Research ServiceWe previously reported that the strains of Escherichia coli O157:H7 (EcO157) that survived longer in austere soil environment lacked expression of curli, a fitness trait linked with intestinal colonization. In addition, the proportion of curli-positive variants of EcO157 decreased with repeated soil exposure. Here we evaluated 84 and 176 clinical strains from outbreaks and sporadic infections in the US, plus 211 animal fecal and environmental strains for curli expression. These shiga-toxigenic strains were from 328 different genotypes, as characterized by multi-locus variable-number tandem-repeat analysis (MLVA). More than half of the fecal strains (human and animal) and a significant proportion of environmental isolates (82%) were found to lack curli expression. EcO157 strains from several outbreaks linked with the consumption of contaminated apple juice, produce, hamburgers, steak and beef were also found to lack curli expression. Phylogenetic analysis of fecal strains indicates curli expression is distributed throughout the population. However, a significant proportion of animal fecal isolates (84%) gave no curli expression compared to human fecal isolates (58%). In addition, analysis of environmental isolates indicated nearly exclusive clustering of curli expression to a single branch of the minimal spanning tree. This indicates that curli expression depends primarily upon the type of environmental exposure and the isolation source, although genotypic differences also contribute to clonal variation in curli. Furthermore, curli-deficient phenotype appears to be a selective trait for survival of EcO157 in agricultural environments.http://journal.frontiersin.org/Journal/10.3389/fcimb.2016.00189/fullE. coliphylogenetic analysisMLVAO157:H7curlispinach
collection DOAJ
language English
format Article
sources DOAJ
author Subbarao Venkata Ravva
Chester Zingapan Sarreal
Michael Bruce Cooley
spellingShingle Subbarao Venkata Ravva
Chester Zingapan Sarreal
Michael Bruce Cooley
Expression of curli by Escherichia coli O157:H7 strains isolated from patients during outbreaks is different from similar strains isolated from leafy green production environments
Frontiers in Cellular and Infection Microbiology
E. coli
phylogenetic analysis
MLVA
O157:H7
curli
spinach
author_facet Subbarao Venkata Ravva
Chester Zingapan Sarreal
Michael Bruce Cooley
author_sort Subbarao Venkata Ravva
title Expression of curli by Escherichia coli O157:H7 strains isolated from patients during outbreaks is different from similar strains isolated from leafy green production environments
title_short Expression of curli by Escherichia coli O157:H7 strains isolated from patients during outbreaks is different from similar strains isolated from leafy green production environments
title_full Expression of curli by Escherichia coli O157:H7 strains isolated from patients during outbreaks is different from similar strains isolated from leafy green production environments
title_fullStr Expression of curli by Escherichia coli O157:H7 strains isolated from patients during outbreaks is different from similar strains isolated from leafy green production environments
title_full_unstemmed Expression of curli by Escherichia coli O157:H7 strains isolated from patients during outbreaks is different from similar strains isolated from leafy green production environments
title_sort expression of curli by escherichia coli o157:h7 strains isolated from patients during outbreaks is different from similar strains isolated from leafy green production environments
publisher Frontiers Media S.A.
series Frontiers in Cellular and Infection Microbiology
issn 2235-2988
publishDate 2016-12-01
description We previously reported that the strains of Escherichia coli O157:H7 (EcO157) that survived longer in austere soil environment lacked expression of curli, a fitness trait linked with intestinal colonization. In addition, the proportion of curli-positive variants of EcO157 decreased with repeated soil exposure. Here we evaluated 84 and 176 clinical strains from outbreaks and sporadic infections in the US, plus 211 animal fecal and environmental strains for curli expression. These shiga-toxigenic strains were from 328 different genotypes, as characterized by multi-locus variable-number tandem-repeat analysis (MLVA). More than half of the fecal strains (human and animal) and a significant proportion of environmental isolates (82%) were found to lack curli expression. EcO157 strains from several outbreaks linked with the consumption of contaminated apple juice, produce, hamburgers, steak and beef were also found to lack curli expression. Phylogenetic analysis of fecal strains indicates curli expression is distributed throughout the population. However, a significant proportion of animal fecal isolates (84%) gave no curli expression compared to human fecal isolates (58%). In addition, analysis of environmental isolates indicated nearly exclusive clustering of curli expression to a single branch of the minimal spanning tree. This indicates that curli expression depends primarily upon the type of environmental exposure and the isolation source, although genotypic differences also contribute to clonal variation in curli. Furthermore, curli-deficient phenotype appears to be a selective trait for survival of EcO157 in agricultural environments.
topic E. coli
phylogenetic analysis
MLVA
O157:H7
curli
spinach
url http://journal.frontiersin.org/Journal/10.3389/fcimb.2016.00189/full
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