Aquaculture in Uganda is rapidly expanding, with Oreochromis niloticus being the predominant farmed species in the Lake Victoria basin. This growth, driven by the need to offset declining wild fish stocks, has intensified production and increased the risk of bacterial diseases such as those caused by Vibrio and Francisella species. These pathogens not only threaten fish health and farm productivity but also raise concerns about antimicrobial resistance, especially in the case of Vibrio, which has public health implications.
This study aims to determine the occurrence, antibiotic susceptibility, and resistance gene profiles of Francisella and Vibrio species isolated from farmed tilapia in the Lake Victoria basin. Ninety fish samples were collected across 9 cage farms and analyzed using microbiological, biochemical, and molecular techniques. No Francisella spp. were isolated from the samples.
Vibrio spp. were successfully isolated, with the following distribution: V. vulnificus (26), V. alginolyticus (4), V. diazotrophicus (4), V. parahaemolyticus (3), and V. cincinnatiensis (3). Antibiotic susceptibility testing revealed that V. alginolyticus and V. parahaemolyticus were only resistant to ampicillin, consistent with their Gram-negative profile. However, V. vulnificus exhibited notable resistance to tetracycline (10 isolates), trimethoprim-sulfamethoxazole (14), cefepime (7), imipenem (4), and gentamicin (1), indicating emerging multidrug resistance.
Conclusion
These preliminary findings highlight the importance of continued surveillance and responsible antibiotic use in aquaculture. The next phase of the study will focus on the molecular characterization of Vibrio species of interest to fish health, including identification of specific virulence factors and antimicrobial resistance genes. This study aims to support biosecurity planning, sustainable antibiotic usage and inform policy for sustainable aquaculture in Uganda.