Theses and Dissertations

ORCID

https://orcid.org/0000-0002-0779-9404

Issuing Body

Mississippi State University

Advisor

Park, Joo Youn

Committee Member

Pruett, Stephen B.

Committee Member

Seo, Keun Seok

Committee Member

Thornton, Justin A.

Date of Degree

8-8-2023

Document Type

Dissertation - Campus Access Only

Major

Veterinary Medical Science

Degree Name

Doctor of Philosophy (Ph.D)

College

College of Veterinary Medicine

Department

College of Veterinary Medicine

Abstract

37.3 million Americans (11.2% of the US population) currently have Type 2 diabetes mellitus (T2DM) with over 1.5 million new cases being diagnosed each year. The multifactorial etiology of the patient having neuropathy, overweight/obesity, foot deformities, ischemia, and infection leads to a condition called diabetic foot ulcer (DFU). One in six patients with a DFU will require amputation with infected DFUs have a 155-fold increased risk of amputation. Staphylococcus aureus is the most common bacteria isolated from severe DFU infections that require amputation. Interestingly, diabetics are more heavily colonized with S. aureus compared to non-diabetics suggesting a unique advantageous adaptation to diabetes. The specifics of the underlying molecular mechanisms and triggers by which S. aureus adapts and thrives in the T2DM patient that increase its pathogenicity and colonization compared to non-diabetics with skin ulcer infections are not fully elucidated. Thus, our studies aimed to identify the key virulence components in the pathogenesis of S. aureus infected DFUs and using that information to develop therapeutics aimed at disrupting these components to increase the success rate of conservative treatment and prevent non-traumatic lower extremity amputations in T2DM patients. Our studies found that several different elevated sugars in T2DM patients can trigger virulence factor production in S. aureus. We also found by comparing several different clinical DFU S. aureus isolates that there are clear differences in the ability of each isolate to cause necrotic infections. And lastly, we identified a possible therapeutic, the amino acid L-arginine, that can help prevent/treat S. aureus infections in the Tallyho diabetic mouse model. In conclusion, we have increased the understanding of the pathogenesis of S. aureus infected DFU and have proposed a possible therapeutic to add to the conservative treatment regimen.

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