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Characterization of a Pathogenic Escherichia coli Strain Derived from Oreochromis spp. Farms Using Whole-Genome Sequencing
Published on: December 23, 2022
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Recent Genetic Changes Affecting Enterohemorrhagic Escherichia coli Causing Recurrent Outbreaks
1National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA.
Microbiology Spectrum
|April 25, 2022
Summary
Closely related E. coli strains have repeatedly caused foodborne outbreaks linked to California produce. Genetic analysis reveals changes in adhesion genes, potentially increasing virulence and persistence. This research aids in identifying dangerous bacterial strains and their reservoirs.
Area of Science:
- Microbiology
- Genomics
- Food Safety
Background:
- Enterohemorrhagic E. coli (EHEC) causes significant human illness, with cattle as the primary reservoir and leafy greens as common vectors.
- Recurrent EHEC outbreaks linked to California produce, particularly from closely related O157:H7 strains, suggest a potential genetic basis for this pattern.
- Understanding the genetic underpinnings of EHEC recurrence and virulence is crucial for effective food safety and public health interventions.
Purpose of the Study:
- To reconstruct the genetic changes in the recent ancestry of recurrent EHEC strains.
- To investigate the potential impact of identified genetic alterations on bacterial properties and disease transmission.
- To explore the utility of genomic surveillance in identifying high-risk bacterial pathogens and their environmental reservoirs.
Main Methods:
- Whole-genome sequencing was employed to analyze the genetic makeup of recurrent EHEC strains.
- Phylogenetic analysis was used to reconstruct the evolutionary history and identify genetic changes.
- Bioinformatic tools were utilized to identify mutations in adhesion-related genes and regulatory elements.
Main Results:
- Several genetic changes were identified in adhesion-related sequences within a short evolutionary period, potentially altering bacterial adhesive properties.
- These alterations may contribute to increased persistence in cattle, higher shedding in feces, and enhanced virulence in humans.
- A specific subclade (Santa Maria) exhibits a mutation in ArsR, suggesting a link to arsenic-contaminated groundwater as a persistent contamination source.
Conclusions:
- Genomic analysis reveals rapid evolution of adhesion factors in recurrent EHEC strains, impacting their pathogenicity.
- Sequencing-based surveillance can identify bacterial constellations indicative of significant public health threats.
- The identification of an arsenic resistance gene mutation provides a potential clue for locating the environmental reservoir of EHEC contamination.
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