Aeromonas hydrophila is a Gram-negative bacterium complex of three species including A.hydrophila sensu stricto, A.bestiarum, and A. salmonicida. A.bestiarum, and A. salmonicida are rarely present in humans.
Aeromonas hydrophila causes a variety of diseases in both fish and human populations. The ubiquitous nature of the bacterium in aquatic environments provides significant opportunity for animals, mainly fish and amphibians to contact and ingest organisms. Aeromonas hydrophila is very toxic to many organisms because of its structure. When it enters the body of fish, amphibians, or humans, it travels via the bloodstream to the first available organ. It produces aerolysin cytotoxic enterotoxin (Act) which is one of the major virulence factors.
In humans, it causes gastroenteritis which can affect anyone, but it most occurs in young children and people who have compromised immune systems or growth problems. This bacterium is linked to two types of gastroenteritis.
The first type is a disease similar to cholera which causes rice- water diarrhea. Mild symptoms include fever and chills, but patients who become overwhelming bacterial infection with Aeromonas hydrophila often exhibit abdominal pain, nausea, vomiting, and diarrhea.
The other type of disease is dysenteric gastroenteritis that causes loose stools filled with blood and mucus. Dysenteric gastroenteritis is the most severe out of the two types, and can last for multiple weeks.
Aeromonas hydrophila is also associated with cellulitis, an infection that causes inflammation in the skin tissue. It also causes diseases such as myonecrosis and eczema in people with compromised immune systems