Aeromonas hydrophila induction method in adult zebrafish (Danio rerio) as animal infection models

Background and Aim: Zebrafish are frequently used as model organisms in scientific research as their genes mirror those of humans. Aeromonas hydrophila bacteria can infect humans and animals, mainly fish. This study aimed to identify the concentration and route of A. hydrophila infection in adult zebrafish. Zebrafish had been used as a challenge test by analyzing their hematological profiles, blood glucose levels, and survival rates. Materials and Methods: Induction of cell supernatant free (CSF) from A. hydrophila bacteria in adult zebrafish was carried out via bath immersion (BI), intraperitoneal injection (IPI), intramuscular injection (IMI), and healthy zebrafish as a control (C). The bacterial concentrations were 10⁷, 10⁹, and 10¹¹colony-forming units (CFU)/mL. At 24 h post-infection, the outcomes of infection were evaluated based on survival rates, hematological profiles, and blood glucose levels. A oneway analysis of variance with a confidence level of 95% was employed to examine the data. Results: In the BI, IPI, and IMI treatment groups, the survival rate of the fish reached a peak of 100%, 22%-100%, and 16%-63%, respectively, compared with the injection technique. In the IMI2 group, a 10⁹CFU/mL bacterial concentration was determined to correspond to the lethal dosage 50. All infection groups had lower erythrocyte and hemoglobin counts but higher leukocyte counts than the control group. The blood sugar levels of the healthy and infected groups were not significantly different. Conclusion: The route of A. hydrophila infection through Intramuscular injection with a concentration of 10⁹CFU/mL indicated a high performance compared to other techniques. This method could be developed as a reproducible challenge test.