Isolation of enterotoxigenic Aeromonas from fish

Area of Science:

• Microbiology
• Fish Pathology
• Food Safety

Background:

• Aeromonas species are common in aquatic environments and can cause disease in fish.
• Enterotoxigenicity in Aeromonas strains is a significant concern for fish health and potentially human health through seafood consumption.

Purpose of the Study:

• To characterize enterotoxigenic Aeromonas species isolated from fish.
• To differentiate between Aeromonas sobria and Aeromonas hydrophila strains regarding their pathogenic potential and toxin production.

Main Methods:

• Isolation and identification of Aeromonas species from fish.
• Assessment of cytotoxic factors, proteolytic activity, and hemolytic patterns on blood agar.
• Evaluation of enterotoxigenicity using the rabbit gut loop assay and suckling mouse test.
• Antigenic characterization of produced enterotoxins.

Main Results:

• Aeromonas sobria strains were isolated only from healthy fish, while Aeromonas hydrophila strains were found in both healthy and moribund fish.
• Both species produced cytotoxic and proteolytic factors. Aeromonas hydrophila exhibited a higher prevalence of dual hemolytic types (92%) compared to Aeromonas sobria (75%).
• A majority of the isolated Aeromonas strains were enterotoxigenic, producing two antigenically related enterotoxins with potentially different mechanisms of action, distinct from E. coli enterotoxins.

Conclusions:

• Aeromonas hydrophila poses a greater pathogenic risk to fish populations than Aeromonas sobria due to its presence in diseased fish and distinct hemolytic profiles.
• The identified enterotoxins from Aeromonas species represent a significant virulence factor contributing to fish enteritis.
• Further research into the specific mechanisms and public health implications of Aeromonas enterotoxins is warranted.