# Identification of Regulatory Loci of Stx2a Cytotoxin Production in Shiga toxin producing Escherichia coli (STEC)

> **NIH NIH SC1** · UNIVERSITY OF TEXAS SAN ANTONIO · 2020 · $374,584

## Abstract

Globally disseminated Shiga toxin (Stx)-producing Escherichia coli (STEC) are notorious for producing a
phage-borne cytotoxin, that is direct mediator of lethal food borne disease. Human morbidity and mortality
remain unacceptably high, as no vaccines and only a limited arsenal of therapeutic or preventive
countermeasures are available. Progression to life-threatening complications during human infection, such as
HUS, is inexorably linked to the production of the most potent cytopathic toxin subtype Stx2a. Hypervirulence as
manifested by increased Stx2a titers has been associated with circulating subpopulations through phylogenetic,
epidemiological and phenotypic linkage. However, there is a dearth of knowledge of the intrinsic genomic
make-up of high-level Stx2a producers. The research objective of this proposal is to apply a systematic and
genome-scale approach to identify causal pathogenome loci responsible for hypervirulent toxin production in
the STEC pathogenome. The central hypothesis is that differences in the isolates' individual Stx2a production
capability are correlated with strain-level sequence variation anchored in both the carried Stx2a-Phage
Sequence Type (PST) and external loci on the phage-hosting STEC pathogenome. The three specific aims to
test this hypothesis are as follows: 1) To catalogue genome-scale variation in clinical STEC specimen through
holistic Whole Genome Sequencing Typing of the STEC core and accessory Stx2a-phage inventory. 2) To
characterize a culture bank of Stx2a lysogen. To reduce the genomic complexity we will create a genomically
defined variant of Stx2a-lysogen cultures. Through lysogenic conversion we will introduce archetypical Stx2a-
PST into the genome background of non-shigatoxigenic E. coli hosts, using among others, atypical stx-
negative STEC and resident gastrointestinal E. coli from our culture collection. Engineered Stx2a-lysogens will
provide a controlled genomic testbed to systematically determine how the Stx2a-PST, phage dosage and
chromosomal location impart Stx2a production, independently or in combination with loci external to the phage
on the respective host chromosomes, and 3) To identify causal genome loci responsible for hypervirulent Stx2a
production. The synergistic determination of phylogroup and Stx2a-production pathotype in wt STEC and
engineered Stx2a-lysogens provides a robust foundation to identify modulatory loci of Stx2a production through
Genome Wide Association Studies. Cultures are phenotyped for Stx2a-phage mobilization efficiency, global
transcriptome changes, Stx2a titers, and in vivo cytotoxicity. Each genotypic variable is tested individually and
in groups of genotypes to account for the participation and interplay of polymorphic Stx2a phage and/or host
loci. This research will provide attractive targets for the development of improved biosurveillance, risk
assessment of suppressive therapeutic anti-Stx2a strategies. Due to the evolutionary conservation among
Stx2a-...

## Key facts

- **NIH application ID:** 9855879
- **Project number:** 1SC1GM135110-01
- **Recipient organization:** UNIVERSITY OF TEXAS SAN ANTONIO
- **Principal Investigator:** Mark Eppinger
- **Activity code:** SC1 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $374,584
- **Award type:** 1
- **Project period:** 2020-05-01 → 2024-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9855879

## Citation

> US National Institutes of Health, RePORTER application 9855879, Identification of Regulatory Loci of Stx2a Cytotoxin Production in Shiga toxin producing Escherichia coli (STEC) (1SC1GM135110-01). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9855879. Licensed CC0.

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