Aeromonas hydrophila

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Aeromonas hydrophila
Aeromonas hydrophila wound infection. Image used with permission by Consultant/HMP Communications.
This typically unheard of species is microscopic, yet can be found anywhere and everywhere that there is water, simply living and waiting to infect a host like you and me.

To better understand the basic characteristics of this species, let's take a closer look at the origin of its name:

Aero- = air/gas (gas producing)
-monas = unicellular organism
hydro- = water
-phila = "lover of" 

Putting that all together, this species is a single-celled aquatic organism. However, it also has a strong tendency to infect those who come in contact with the contaminated water, especially fish, but also other organisms such as birds, frogs and humans. It secretes several toxins that may cause tissue damage, sometimes forming a fatal gas gangrene in the process. It has also been referred to as "Motile Aeromonas Septicemia," "Hemorrhagic Septicemia," "Ulcer Disease," and "Red-Sore Disease". These names imply its tendency to cause bacterial infection throughout different areas of the host where the bacteria has lodged itself. It is commonly the cause of gastroenteritis, but can also cause bacteremia, meningitis, wound infections, and lung infections. In intestinal infections, the bacteria typically causes short-term fever and severe diarrhea, but it can become fatal if it infects other areas of the body such as an open wound.                            
Gram stain of Aeromonas hydrophilaThroughout this website you can learn more about how this species taxonomically relates to other organisms in evolution, as recent discoveries in molecular biology have impacted its current classification. Then learn about where this organism can be found, both as a free-living organism and as a bacterial pathogen. Its unique adaptations allow it to persist through a variety of these environments on its way to its host. Once inside the host, it is able to exploit itself because of these adaptations and become pathogenic. There are many mechanisms including both cytonic enterotoxins and cytoxic enterotoxins that act as virulence factors. The strong metabolic nutrition and reproductive mechanisms of the species, A. hydrophila, allow it to interact with its host while also being able to strive as a free-living organism. As a pathogenic host, it can affect many different populations of people all around the world, but there are certain risk factors and protection policies that bring the issue to concern for public health. For such a small and "simple" prokaryote, this species is incredibly complex and, still, much about it remains unknown. Thank you to all who have contributed to the knowledge base of this website.

Kelly Brusky
University of Wisconsin - La Crosse
BIO 203 - Spring 2013

To learn more about the author, look at the contact page. Otherwise, proceed to the first page on classification.

This website is part of a larger project at These websites have been compiled over the years by other undergraduate students at UW-La Crosse. Return to this home page to learn about other organisms.