Aeromonas hydrophila
Josh Martin

The Aeromonas hydrophila bacterium is found in all freshwater environments and in brackish water (2). It is a Gram negative rod that has polar flagella and is a facultative anaerobe. It is also oxidase-positive and glucose-fermenting. The bacterium is about 0.3-1.0 um in diameter and 1.0-3.5 um in length and has optimal growth at 28C but can also grow at the extremes from 4C to 37C (3).

The bacterium was first discovered in 1962 while researchers, one named Hoshina, T., were looking at the causes of the eel and fish disease “red fin.” I can’t find out who exactly discovered it or how they named it though. In fish and other marine life it has been associated with several diseases: tail rot, fin rot, and haemorrahagic septicaemias.

In humans, the bacterium is transmitted through fecal-oral transmission, contact with contaminated water, food, soil, feces, and ingestion of contaminated fish or reptiles (1). The most common way of catching the bacterium is through an open wound in contaminated water. The mild symptoms of the infection include fever and chills. The people that have the infection and it becomes septic, the symptoms include abdominal pain, nausea, vomiting, and diarrhea. There are three different types of wounds that can come from aeromonas hydrophila in human: cellulitis, myonecrosis, and ecthyma gangrenosum. Cellulitis is the most common type and it is the inflammation of the subcutaneous tissue and is shown in a picture below (3). The other two, myonecrosis and ecthyma gangrenosum, are less common but have worse results. Cellulitis, with the proper medication, will pass with minimal damage while the others cause amputations and sometimes can be fatal. The last two pictures below show them. This microbe is resistant to penicillin, ampicillin, carbenicillin and ticarcillin but is susceptible to expanded- and broad-spectrum cephalosporins, aminoglycosides, carbapenems, chloramphenicol, tetracycline, trimethoprim-sulfamethoxazole and the quinolones (1).

The reason this bacterium interested me is because I swim a lot in my own creek on my farm and in many other freshwater rivers and lakes. Also, one of my dad’s friends actually got cellulitis from a cut and they found out that this little guy was the culprit.

Aeromonas hydrophila (3)

Cellulitis (3)

Myonecrosis and Ecthyma Gangrenosum (3)


(1) Health Canada, Material Safety Data Sheet – Infectious Substance, February 3th, 2004
(2) Center for Food Safety and Applied Nutrition, Aeromonas Hydrophila, February 5th, 2004
(3) Hayes, John, Aeromonas hydrophila, February 6th, 2004

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.


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