Aeromonas Hydrophila and Related Bacteria

Aeromonas hydrophila and Related Bacteria


Aeromonas hydrophila(pronounced "air-oh-moan-ass" "high-drof-ill-uh") is abacterium that is commonly found in freshwater environments and in brackishwater. Although there has never been a known outbreak or illness from Aeromonashydrophila, it has been isolated from sprouted seeds. Fortunately, A. hydrophila is susceptible to a 1% solution ofsodium hypochlorite. Though I am unaware of any studies undertaken to remove thepathogen from seed, the FDA recommended 2% solution of calcium hypochlorite as asoak should have an effect on reducing or eliminating this potentially harmfulbacterial from sprouting seed.


Some, but not all, strainsof A. hydrophila are capable of causing illness in humans by infectingopen wounds and possibly by ingesting the organisms in food or water. Severalrelated species, Aeromonas caviae, Aeromonas sobria and Aeromonasveronii may also be capable of causing illness in humans.


At the present time, thereis controversy as to whether or not these organisms are able to cause humangastrointestinal illness. Volunteer human feeding studies, even with highnumbers of cells, have not produced illness. However, the organism has beenpresent in the stools of individuals with diarrhea when no other entericpathogens could be found. This suggests that some variants of these organismshave the ability to cause disease. The frequency of the disease is unknown. Itusually occurs as an individual case or as a small number of cases rather thanin large outbreaks. To date, there has not been a well-documented outbreak ofthe disease.

Nature of theDisease

A. hydrophila, A.caviae and A. sobria may cause gastroenteritis in apparentlyhealthy individuals or septicemia in individuals with weak or defective immunesystems or those with malignancies. Two types of gastrointestinal disease havebeen associated with A. hydrophila: a watery diarrhea and adysentery-like diarrheal disease characterized by loose stools containing bloodand mucus. On rare occasions, the dysentery-like disease may be severe and lastfor weeks. These organisms have been known to cause a generalized infection andspread throughout the body in persons with weak or defective immune systems,malignancies and other preexisting diseases. In such individuals, a generalizedinfection can be life-threatening. The infectious dose is unknown, but it ispossible that low numbers of organisms may cause illness.

Foods AssociatedWith Illness

Sproutshave not been associated with A.hydrophila, thoughit still should be a concern to growers because it has been found on sproutingseed. It could also travel onto sprouts by production workers with poor handwashing or personal hygiene practices.  Ithasfrequently been found in fish and shellfish. It has also been found in red meats(beef, pork, lamb) and poultry. Since these organisms are so common, it isassumed that not all strains are able to cause disease.