Special Issue "Molecular Basis and the Pathogenesis of Enterohemorrhagic Escherichia coli Infections"

A special issue of Toxins (ISSN 2072-6651). This special issue belongs to the section "Bacterial Toxins".

Deadline for manuscript submissions: closed (30 September 2019).

Special Issue Editor

Dr. Kim Stanford
E-Mail Website
Guest Editor
Livestock Systems Section, Alberta Agriculture and Forestry, Lethbridge, AB T1J 4V6, Canada
Interests: food and feed-borne pathogens; Escherichia coli; ergot alkaloids
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Shiga toxin-producing Escherichia coli (STEC) are food-borne pathogens implicated in sporadic as well as national and international outbreaks of disease. Cattle and other ruminants are identified reservoirs of these organisms, which are erratically shed in feces. Although cattle are colonized with a diverse population of STEC, a relatively small proportion has been linked to human disease. A central question is how best to conclusively identify Escherichia coli that will lead to human disease. The abundance and persistence of Escherichia coli strains in animal hosts and the environment have been proposed as factors affecting the likelihood of strain pathogenicity, but what factors contribute to strain abundance and persistence? What virulence or other factors determine the pathogenicity of Escherichia coli? In addition, the genetic plasticity of Escherichia coli leading to the loss or gain of Shiga toxins and other virulence factors increases the difficulty of identifying potential pathogens, especially among non-O157 E. coli.

The focus of this Special Issue of Toxins will be on the pathogenicity of enterohemorrhagic Escherichia coli including: factors increasing the survival, abundance or persistence in the environment or animal hosts; the molecular basis of infections; molecular or other assays for the detection of E. coli causing disease; possible interventions to decrease the production of Shiga toxins or other virulence factors and control disease. The ultimate aim would be a reduction in future STEC outbreaks and improved outcomes for STEC patients.

Dr. Kim Stanford
Guest Editor

Manuscript Submission Information

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Keywords

  • Enterohemorrhagic Escherichia coli
  • Shiga toxins
  • virulence factors
  • environmental persistence
  • detection
  • human infection
  • interventions

Published Papers (5 papers)

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Research

Open AccessArticle
Pre-Harvest Survival and Post-Harvest Chlorine Tolerance of Enterohemorrhagic Escherichia coli on Lettuce
Toxins 2019, 11(11), 675; https://doi.org/10.3390/toxins11110675 - 19 Nov 2019
Abstract
In the field, foodborne pathogens such as enterohemorrhagic Escherichia coli (EHEC) are capable of surviving on produce over time, yet little is known about how these pathogens adapt to this environment. To assess the impact of pre-harvest environmental conditions on EHEC survival, we [...] Read more.
In the field, foodborne pathogens such as enterohemorrhagic Escherichia coli (EHEC) are capable of surviving on produce over time, yet little is known about how these pathogens adapt to this environment. To assess the impact of pre-harvest environmental conditions on EHEC survival, we quantified survival on romaine lettuce under two relative humidity (75% and 45%) and seasonal conditions (March and June). Greenhouse-grown lettuce was spray-inoculated with EHEC and placed in a growth chamber, mimicking conditions typical for June and March in Salinas Valley, California. Bacteria were enumerated on days 0, 1, 3, and 5 post-inoculation. Overall, we found that the effect of relative humidity on EHEC survival depended on the seasonal conditions. Under June seasonal conditions, higher relative humidity led to lower survival, and lower relative humidity led to greater survival, five days post-inoculation. Under March seasonal conditions, the impact of relative humidity on EHEC survival was minimal over the five days. The bacteria were also tested for their ability to survive a chlorine decontamination wash. Inoculated lettuce was incubated under the June 75% relative humidity conditions and then washed with a 50 ppm sodium hypochlorite solution (40 ppm free chlorine). When incubated under June seasonal conditions for three to five days, EHEC strains showed increased tolerance to chlorine (adj. p < 0.05) compared to chlorine tolerance upon inoculation onto lettuce. This indicated that longer incubation on lettuce led to greater EHEC survival upon exposure to chlorine. Subsequent transcriptome analysis identified the upregulation of osmotic and oxidative stress response genes by EHEC after three and five days of incubation on pre-harvest lettuce. Assessing the physiological changes in EHEC that occur during association with pre-harvest lettuce is important for understanding how changing tolerance to post-harvest control measures may occur. Full article
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Open AccessArticle
Epidemiology of Shiga Toxin-Producing Escherichia coli O157 in the Province of Alberta, Canada, 2009–2016
Toxins 2019, 11(10), 613; https://doi.org/10.3390/toxins11100613 - 22 Oct 2019
Abstract
Shiga toxin-producing Escherichia coli (STEC) infections are the product of the interaction between bacteria, phages, animals, humans, and the environment. In the late 1980s, Alberta had one of the highest incidences of STEC infections in North America. Herein, we revisit and contextualize the [...] Read more.
Shiga toxin-producing Escherichia coli (STEC) infections are the product of the interaction between bacteria, phages, animals, humans, and the environment. In the late 1980s, Alberta had one of the highest incidences of STEC infections in North America. Herein, we revisit and contextualize the epidemiology of STEC O157 human infections in Alberta for the period 2009–2016. STEC O157 infections were concentrated in large urban centers, but also in rural areas with high cattle density. Hospitalization was often required when the Shiga toxin genotype stx2a stx2c was involved, however, only those aged 60 years or older and infection during spring months (April to June) independently predicted that need. Since the late 1980s, the rate of STEC O157-associated hemolytic uremic syndrome (HUS) in Alberta has remained unchanged at 5.1%, despite a marked drop in the overall incidence of the infection. While Shiga toxin genotypes stx1a stx2c and stx2a stx2c seemed associated with HUS, only those aged under 10 years and infection during spring months were independently predictive of that complication. The complexity of the current epidemiology of STEC O157 in Alberta highlights the need for a One Health approach for further progress to be made in mitigating STEC morbidity. Full article
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Open AccessArticle
Contribution and Interaction of Shiga Toxin Genes to Escherichia coli O157:H7 Virulence
Toxins 2019, 11(10), 607; https://doi.org/10.3390/toxins11100607 - 18 Oct 2019
Abstract
Escherichia coli O157:H7 is the predominant cause of diarrhea-associated hemolytic uremic syndrome (HUS) worldwide. Its cardinal virulence traits are Shiga toxins, which are encoded by stx genes, the most common of which are stx1a, stx2a, and stx2c. The toxins these genes [...] Read more.
Escherichia coli O157:H7 is the predominant cause of diarrhea-associated hemolytic uremic syndrome (HUS) worldwide. Its cardinal virulence traits are Shiga toxins, which are encoded by stx genes, the most common of which are stx1a, stx2a, and stx2c. The toxins these genes encode differ in their in vitro and experimental phenotypes, but the human population-level impact of these differences is poorly understood. Using Shiga toxin-encoding bacteriophage insertion typing and real-time polymerase chain reaction, we genotyped isolates from 936 E. coli O157:H7 cases and verified HUS status via chart review. We compared the HUS risk between isolates with stx2a and those with stx2a and another gene and estimated additive interaction of the stx genes. Adjusted for age and symptoms, the HUS incidence of E. coli O157:H7 containing stx2a alone was 4.4% greater (95% confidence interval (CI) −0.3%, 9.1%) than when it occurred with stx1a. When stx1a and stx2a occur together, the risk of HUS was 27.1% lower (95% CI −87.8%, −2.3%) than would be expected if interaction were not present. At the population level, temporal or geographic shifts toward these genotypes should be monitored, and stx genotype may be an important consideration in clinically predicting HUS among E. coli O157:H7 cases. Full article
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Open AccessArticle
Bacteriocin Occurrence and Activity in Escherichia coli Isolated from Bovines and Wastewater
Toxins 2019, 11(8), 475; https://doi.org/10.3390/toxins11080475 - 15 Aug 2019
Abstract
The increasing prevalence of antimicrobial resistant (AMR) E. coli and related Enterobacteriaceae is a serious problem necessitating new mitigation strategies and antimicrobial agents. Bacteriocins, functionally diverse toxins produced by most microbes, have long been studied for their antimicrobial potential. Bacteriocins have once again [...] Read more.
The increasing prevalence of antimicrobial resistant (AMR) E. coli and related Enterobacteriaceae is a serious problem necessitating new mitigation strategies and antimicrobial agents. Bacteriocins, functionally diverse toxins produced by most microbes, have long been studied for their antimicrobial potential. Bacteriocins have once again received attention for their role as probiotic traits that could mitigate pathogen burden and AMR bacteria in livestock. Here, bacteriocins were identified by activity screening and whole-genome sequencing of bacteriocin-producers capable of inhibiting bovine and wastewater E. coli isolates enriched for resistance to cephalosporins. Producers were tested for activity against shiga toxin-producing E. coli (STEC), AMR E. coli, and related enteric pathogens. Multiple bacteriocins were found in 14 out of 90 E. coli isolates tested. Based on alignment within BACTIBASE, colicins M, B, R, Ia, Ib, S4, E1, E2, and microcins V, J25, and H47, encoded by identical, variant, or truncated genes were identified. Although some bacteriocin-producers exhibited activity against AMR and STEC E. coli in agar-based assays, most did not. Despite this idiosyncrasy, liquid co-cultures of all bacteriocinogenic isolates with luciferase-expressing generic (K12) or STEC E. coli (EDL933) resulted in inhibited growth or reduced viability. These abundant toxins may have real potential as next-generation control strategies in livestock production systems but separating the bacteriocin from its immunity gene may be necessary for such a strategy to be effective. Full article
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Open AccessArticle
Virulence Characteristics and Antimicrobial Resistance Profiles of Shiga Toxin-Producing Escherichia coli Isolates from Humans in South Africa: 2006–2013
Toxins 2019, 11(7), 424; https://doi.org/10.3390/toxins11070424 - 19 Jul 2019
Abstract
Shiga toxin-producing Escherichia coli (STEC) isolates (N = 38) that were incriminated in human disease from 2006 to 2013 in South Africa were characterized by serotype, virulence-associated genes, antimicrobial resistance and pulsed-field gel electrophoresis (PFGE). The isolates belonged to 11 O:H serotypes. STEC [...] Read more.
Shiga toxin-producing Escherichia coli (STEC) isolates (N = 38) that were incriminated in human disease from 2006 to 2013 in South Africa were characterized by serotype, virulence-associated genes, antimicrobial resistance and pulsed-field gel electrophoresis (PFGE). The isolates belonged to 11 O:H serotypes. STEC O26:H11 (24%) was the most frequent serotype associated with human disease, followed by O111:H8 (16%), O157:H7 (13%) and O117:H7 (13%). The majority of isolates were positive for key virulence-associated genes including stx1 (84%), eaeA (61%), ehxA (68.4%) and espP (55%), but lacked stx2 (29%), katP (42%), etpD (16%), saa (16%) and subA (3%). stx2 positive isolates carried stx2c (26%) and/or stx2d (26%) subtypes. All pathogenicity island encoded virulence marker genes were detected in all (100%) isolates except nleA (47%), nleC (84%) and nleD (76%). Multidrug resistance was observed in 89% of isolates. PFGE revealed 34 profiles with eight distinct clusters that shared ≥80% intra-serotype similarity, regardless of the year of isolation. In conclusion, STEC isolates that were implicated in human disease between 2006 and 2013 in South Africa were mainly non-O157 strains which possessed virulence genes and markers commonly associated with STEC strains that have been incriminated in mild to severe human disease worldwide. Improved STEC monitoring and surveillance programs are needed in South Africa to control and prevent STEC disease in humans. Full article
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