Theses and Dissertations
ORCID
https://orcid.org/0000-0002-2529-4696
Advisor
Tekedar, Hasan C.
Committee Member
Lawrence, Mark L.
Committee Member
Hanson, Larry A.
Committee Member
Reichley, Stephen R.
Date of Degree
12-12-2025
Original embargo terms
Embargo 2 years
Document Type
Graduate Thesis - Open Access
Major
Veterinary and Biomedical Sciences (Infectious Diseases)
Degree Name
Master of Science (M.S.)
College
College of Veterinary Medicine
Department
Department of Comparative Biomedical Sciences
Abstract
Antimicrobial resistance (AMR) is a major concern in aquaculture and public health. This study applied adaptive laboratory evolution to examine how Edwardsiella ictaluri and Aeromonas hydrophila adapt under prolonged antibiotic exposure. E. ictaluri evolved resistance to colistin sulfate through large-scale genomic changes, including deletion of the major virulence factor type III secretion system, leading to altered growth and increased biofilm formation. In A. hydrophila, both Minimal Inhibitory Concentration (MIC)-based and Two-Fold method strategies rapidly produced resistance to oxytetracycline dihydrate (OTC). Phenotypic assays revealed fitness costs, altered stress tolerance, cross-resistance, and collateral sensitivity to other antibiotics. These findings highlight that antibiotic adaptation generates distinct evolutionary trajectories, often accompanied by physiological trade-offs. The results emphasize the risks of extended use of antibiotics in aquaculture while suggesting ALE as a valuable tool for understanding resistance mechanisms and associated physiological adaptations.
Sponsorship (Optional)
Global Center for Aquatic Health and Food Security
Recommended Citation
Aishy, Rideeta Islam, "Adaptive evolutionary insights into antimicrobial resistance and fitness costs in aquaculture pathogens" (2025). Theses and Dissertations. 6825.
https://scholarsjunction.msstate.edu/td/6825
