# Molecular mechanisms of lytic bacteriophage infection of enterococci

> **NIH NIH F31** · UNIVERSITY OF COLORADO DENVER · 2022 · $7,814

## Abstract

PROJECT SUMMARY
In recent decades there has been a rapid decline in effective antibiotic therapies and an increase in multidrug-
resistant (MDR) bacterial infections. One common MDR pathogen is the Gram-positive intestinal bacterium
Enterococcus faecalis which resists many antibiotics including “last-line-of-defense” drugs such as
vancomycin. MDR enterococci can expand in the intestine in individuals undergoing broad-spectrum antibiotic
therapy. This expansion can lead to E. faecalis translocation to the bloodstream, sepsis, and further shedding
of the bacterium, thus perpetuating these hospital-acquired infections. One potential strategy to combat MDR
enterococci is the use of bacteriophages (phages). Phages are viruses that infect and kill bacteria with high
specificity. Phage infection relies on binding to the bacterial cell surface, ejection of phage DNA into the
bacterial cell, replication of the phage genome, and viral particle release from the cell. The use of phages as
therapeutics raises concern similar to antibiotic use; bacteria will become resistant to infection, diminishing
therapeutic efficacy. Thus, before phages can become a standard clinical therapy, we must clearly understand
the specific mechanisms used by phages to infect bacteria and how bacteria respond to phage infection. To
begin to elucidate the mechanisms used by phages during infection, I challenged E. faecalis with lytic phages
and found that the enterococcal polysaccharide antigen is used for initial phage adsorption to various E.
faecalis strains, including strains that the phage cannot successfully infect. Along with this, I have shown that
the presence of a mobile plasmid in E. faecalis restricts phage infection. The goals of this project are to fill key
gaps in our basic knowledge of phage-bacteria interactions and to provide insights into the mechanisms that
influence the outcomes of phage infection, which will be beneficial knowledge for applied phage therapies. This
project encompasses the following two Specific Aims: Aim 1: Identify the receptor that promotes DNA entry
of Epa-dependent phages. This will be addressed through complementary biochemical assays to identify the
receptor that promotes phage DNA entry into E. faecalis. Aim 2: Define the genetic basis of endogenous
plasmids in restricting enterococcal phage infection. Here, I will use genetic approaches to identify a
novel, enterococcal anti-phage restriction mechanism encoded on a mobile plasmid. These experiments will
reveal new insights into the mechanisms that dictate enterococcal phage recognition and infection that will
ultimately aid in the development of informed phage therapies. In doing so, my results will expand our basic
knowledge surrounding enterococcal cell biology during phage infection and potentially identify new targets for
anti-enterococcal therapies.

## Key facts

- **NIH application ID:** 10532141
- **Project number:** 5F31AI157050-02
- **Recipient organization:** UNIVERSITY OF COLORADO DENVER
- **Principal Investigator:** Cydney N Johnson
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $7,814
- **Award type:** 5
- **Project period:** 2021-08-01 → 2022-08-24

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10532141

## Citation

> US National Institutes of Health, RePORTER application 10532141, Molecular mechanisms of lytic bacteriophage infection of enterococci (5F31AI157050-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10532141. Licensed CC0.

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