Prevalence, virulence genes, and antibiogram profile of Aeromonas hydrophila isolated from diseased Oreochromis niloticus and Clarias gariepinus in Dakahlia province, Egypt

Document Type : Original Articles


1 Fish diseases and management department, Animal Health Research Institute(Mansoura branch) Agricultural Research Center

2 Fish diseases and management department, Faculty of Veterinary Medicine, Mansoura University

3 Department of Internal Medicine, Infectious and Fish diseases, Faculty of Veterinary Medicine , Mansoura University


Objective: To determine the prevalence and characterization of Aeromonas hydrophila in Oreochromis niloticus and Clarias gariepinus obtained from a private fish farm and Bahar Hados drainage in Manzala, Dakahlia governorate, Egypt, during the winter and summer season of 2021.

Design: a prevalence study.

Fish: Two-hundred moribund and freshly dead fish were used in this study.

Procedures: Fish samples were examined for clinical and postmortem changes. The liver, kidney, and gills were collected for histopathological, bacteriological examination, and identification of bacterial isolates and their virulence genes by PCR. Additionally, antimicrobial susceptibility of the retrieved isolates was also investigated.

Results: There were hemorrhages on different parts of the fish body with abdominal distention, and congested liver, kidney, and spleen. The highest prevalence of A. hydrophila was recorded in the summer season (69.4%). The result showed the positive detection for (hlyA), (AerA), and (Lip) genes in the summer season and (AerA), and (Lip) genes in the winter season for wild and cultured O. niloticus. All virulence genes were detected in Cl. gariepinus except for (hylA) was completely absent in the winter season in wild one. Ast was completely absent. A. hydrophila isolates were completely resistant to erythromycin and amoxicillin but were sensitive to ciprofloxacin and florfenicol.

Conclusion and clinical relevance: The presence of A.hydrophila with virulence potential in freshwater fish may significantly threaten public health. Proper action should be taken into consideration through administering appropriate antibiotics such as florfenicol and ciprofloxacin and by improving the diagnostic standard using molecular techniques.


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