Aeromonas hydrophila also has a symbiotic relationship as gut flora inside of certain leeches, such as Hirudo medicinalis.

A. hydrophila, A. caviae, and A. sobria are all considered to be opportunistic pathogens, meaning they rarely infect healthy individuals.

T3SS is a specialized protein secretion machinery that exports virulence factors directly to host cells.

ADP-ribosylation toxin is one of the effector molecules secreted by several pathogenic bacteria and translocated through the T3SS and delivered into the host cytoplasm, which leads to interruption of the NF-κB pathway, cytoskeletal damage, and apoptosis.

[5] Aeromonas hydrophila is associated with diseases mainly found in freshwater fish and amphibians, because these organisms live in aquatic environments.

It is linked to a disease found in frogs called red leg, which causes internal, sometimes fatal hemorrhaging.

One of the diseases it can cause in humans, gastroenteritis, occurs mostly in young children and people who have compromised immune systems or growth problems.

[10] Antibiotics such as chloramphenicol, florfenicol, tetracycline, sulfonamide, nitrofuran derivatives, and Pyridinecarboxylic acids are used to eliminate and control the infection of A. hydrophila.

Paul et al. (2021)[11] isolated and identified probiotic Bacillus subtilis strain WS1A that can inhibit the growth of pathogenic Aeromonas in fish.

[11][12] Fish (Labeo rohita) fed with extracellular products of Bacillus subtilis strain WS1A develop disease resistance against motile Aeromonas septicemia.

This strain was isolated from marine sponge of Saint Martin's Island in the Bay of Bengal, Bangladesh.