# Decoding the clinical impact of the recent evolution of metronidazole resistance on Clostridium difficile infection.

> **NIH NIH R01** · TEXAS A&M UNIVERSITY HEALTH SCIENCE CTR · 2024 · $183,766

## Abstract

In patients with Clostridioides difficile infection (CDI) treated with the most commonly used
antibiotic, vancomycin (VAN), sustained clinical cure (SCC) rates can be as low as 50-60%.
Methods to identify C. difficile strains likely to fail VAN therapy are needed. Our long-term goal is
to develop clinically relevant CDI susceptibility measures predictive of patient outcomes. The
parent grant explores and identifies antimicrobial resistance contributing to these poor failure
rates. This project will expand these investigations into a newly identified resistance mechanism,
biofilms. Infections caused by biofilm-producing bacteria are notoriously difficult to treat due to
biofilms’ inherent increase in antibiotic resistance. Recently discovered by our group and others,
C. difficile can be successfully grown in multispecies biofilms using representative gut microbiome
species leading to a higher likelihood of in vitro CDI recurrence. Sessile C. difficile cells embedded
in biofilm can have VAN MICs that are 100-times or higher than planktonic (non-biofilm) C. difficile.
However, no studies have investigated a large number of clinical strains to assess the variance
in C. difficile biofilm quantity among clinical strains or an effect on patient outcomes. Our
hypothesis is that higher biofilm production decreases SCC rates. The central hypothesis will be
supported by two specific aims: Aim 1 will determine the variance in biofilm formation among
clinical C. difficile strains stratified by ribotype. This aim tests the hypothesis that biofilm
development will be variable amongst C. difficile strains within ribotype groupings. Quantification
of biofilms using the traditional crystal violet (CV) technique is ongoing with an innovative ATP
bioluminescent biofilm technique developed as part of this proposal. Aim 2 will determine if biofilm
quantity predicts VAN minimum biofilm eradication concentrations (MBEC) or sustained clinical
cure (SCC) in hospitalized CDI patients treated with VAN. This aim tests the critical hypothesis
that C. difficile biofilm formation is relevant in determining SCC. Biofilm quantitation will be
evaluated in multivariate models to determine whether biofilm quantitation is predictive of MBEC
values, SCC or both. We expect these findings will provide, for the first time, a biofilm quantity
and VAN MBEC susceptibility measure that is predictive of poor patient outcomes. The proposed
research will benefit the parent grant research by providing a tool to assess whether VAN
resistance caused by biofilm-producing C. difficile strains impacts patient outcomes. These
studies lay the foundation for the candidate to further expand into clinical microbiology
translational research.

## Key facts

- **NIH application ID:** 11015520
- **Project number:** 3R01AI139261-06S1
- **Recipient organization:** TEXAS A&M UNIVERSITY HEALTH SCIENCE CTR
- **Principal Investigator:** Kevin W Garey
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $183,766
- **Award type:** 3
- **Project period:** 2018-08-20 → 2025-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/11015520

## Citation

> US National Institutes of Health, RePORTER application 11015520, Decoding the clinical impact of the recent evolution of metronidazole resistance on Clostridium difficile infection. (3R01AI139261-06S1). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/11015520. Licensed CC0.

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