Date of Award

Spring 5-10-2019

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Animal Sciences

Advisor

Anne Lichtenwalner

Second Committee Member

Juan Romero

Third Committee Member

Con Sullivan

Additional Committee Members

Sally Molloy

Abstract

Caseous lymphadenitis (CL) is a chronic bacterial infection caused by Corynebacterium pseudotuberculosis (C. pseudoTB) that affects small ruminants. This disease has a worldwide prevalence and results in significant economic losses to the sheep and goat industries. Antibiotics have had limited success in treating CL, due to the difficulty of penetrating the dry, thick-walled abscesses that characterize this disease. Essential oils are complex bioactive compounds that have been increasingly explored as sources of antimicrobial activity. Due to the nature of these oils, tissue and wood penetration may be possible, enabling topical and environmental treatment (e.g.; disinfectants of farm surfaces, such as feeders or shearing equipment). The purpose of this project was to evaluate certain essential oil components (EOCs) with known antibacterial properties for their bactericidal effects on C. pseudoTB using a standard disk diffusion assay. The most effective inhibition of C. pseudoTB growth in vitro was due to β-citronellol, carvacrol, thymol, and trans-cinnamaldehyde. These EOCs were able to inhibit C. pseudoTB growth at concentrations as low as 10 mg/ml. Essential oils and their components can also have toxic effects on eukaryotic cells. For this reason, a cell viability assay on a line of mammalian fibroblast cells (Buffalo rat liver cells) was conducted to evaluate the cytotoxicity of the EOCs that were most effective at inhibiting C. pseudoTB growth. Based on direct microscopic observations, EOCs damaged mammalian cells; this was not reflected in the cell viability assay. Therefore, further research is needed on the toxicity of these components before use in vivo.

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