The kinds of Aeromonas hydrophila - 1

Aeromonas hydrophila consist of :

1. Name of the Organism:
Aeromonas hydrophila, Aeromonas caviae, Aeromonas sobria & (Aeromonas veronii?)

Aeromonas hydrophila is a species of bacterium that is present in all freshwater environments and in brackish water. Some strains of A. hydrophila are capable of causing illness in fish and amphibians as well as in humans who may acquire infections through open wounds or by ingestion of a sufficient number of the organisms in food or water.
Not as much is known about the other Aeromonas spp., but they too are aquatic microorganisms and have been implicated in human disease.

2. Nature of Acute Disease:
A. hydrophila may cause gastroenteritis in healthy individuals or septicemia in individuals with impaired immune systems or various malignancies.
A. caviae and A. sobria also may cause enteritis in anyone or septicemia in immunocompromised persons or those with malignancies.



3. Nature of Disease:
At the present time, there is controversy as to whether A. hydrophila is a cause of human gastroenteritis. Although the organism possesses several attributes which could make it pathogenic for humans, volunteer human feeding studies, even with enormous numbers of cells (i.e. 10^11), have failed to elicit human illness. Its presence in the stools of individuals with diarrhea, in the absence of other known enteric pathogens, suggests that it has some role in disease.

Likewise, A. caviae and A. sobria are considered by many as "putative pathogens," associated with diarrheal disease, but as of yet they are unproven causative agents.
Two distinct types of gastroenteritis have been associated with A. hydrophila: a cholera-like illness with a watery (rice and water) diarrhea and a dysenteric illness characterized by loose stools containing blood and mucus. The infectious dose of this organism is unknown, but SCUBA divers who have ingested small amounts of water have become ill, and A. hydrophila has isolated from their stools.
A general infection in which the organisms spread throughout the body has been observed in individuals with underlying illness (septicemia).

4. Diagnosis of Human Illness:
A. hydrophila can be cultured from stools or from blood by plating the organisms on an agar medium containing sheep blood and the antibiotic ampicillin. Ampicillin prevents the growth of most competing microorganisms. The species identification is confirmed by a series of biochemical tests. The ability of the organism to produce the enterotoxins believed to cause the gastrointestinal symptoms can be confirmed by tissue culture assays.