Author ORCID Identifier

https://orcid.org/0009-0006-3900-6014

Date Available

8-15-2027

Year of Publication

2025

Document Type

Master's Thesis

Degree Name

Master of Science (MS)

College

Agriculture, Food and Environment

Department/School/Program

Veterinary Science

Faculty

Carrie L. Shaffer

Abstract

Rhodococcus equi is a soil-dwelling, respiratory pathogen that causes severe or fatal pneumonia in foals and remains the most common cause of granulomatous bronchopneumonia in young horses. Colonization plasticity exhibited by R. equi is highlighted by the ability of the bacterium to act as an opportunistic and zoonotic pathogen in other species, including immunocompromised humans. Currently, we lack a complete understanding of the bacterial factors that are required for host colonization and pathogenicity. Here, we used a combination of molecular approaches and advanced cryo-electron tomography to analyze the R. equi cell surface and delineate pathogenicity determinants that can be targeted in new treatment and prevention strategies. We identified several cell surface structures and outer membrane features related to other mycobacterial-like bacterial species, highlighting evolutionary paradigms. Our findings revealed unique characteristics of the R. equi cell surface, including the discovery of lipid tubes derived from a single bilayer mycobacterial-like outer membrane. Additionally, we analyzed the role of R. equi polysaccharide capsule biogenesis determinants in mediating biofilm formation and interactions with host epithelial and macrophage-like cells. Collectively, insights garnered from these studies offer promising avenues for the development of novel therapeutics and vaccine interventions designed to combat R. equi infection and disease.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2025.383

Funding Information

This project was supported by the United States Department of Agriculture through the Kentucky Agricultural Experiment Station (HATCH Project Number KY014069) and the National Institutes of Health (Grant P20GM130456).

Available for download on Sunday, August 15, 2027

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