Aeromonas hydrophila
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| Aeromonas hydrophila (Chester, 1901) Stanier, 1943 |
Aeromonas hydrophila is a heterotrophic, gram-negative bacterium, mainly found in areas where the climate is really warm. This bacterium can also be found in fresh, salt, marine, estuarine, chlorinated, and un-chlorinated water. Aeromonas hydrophila can survive in aerobic and anaerobic environments. This bacterium can digest materials such as gelatin, and hemoglobin. Aeromonas hydrophila was isolated from humans and animals until the 1950s. This bacterium is the most well known of the six species of Aeromonas. It is also very hard to kill, because it is a very resistant bacterium. Aeromonas hydrophila is resistant to chlorine, refrigeration or cold temperatures (in fact Aeromonas hydrophila has been known to survive in temperatures as low as four degrees Celsius).
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[edit] Structure
Aeromonas hydrophila are rod-shaped, meaning they are from the bacterium type Bacillus. They usually grow from .3 to 1 micrometer in width, and 1 to 3 micrometers in length. Aeromonas hydrophila does not start its life as an endospore, and can grow in temperatures as low as four degrees Celsius. These bacteria move around using their polar flagella. Because of its structure and the type of bacteria that it is, Aeromonas hydrophila can only be identified by using a gram stain, which is a technique used to identify bacteria, stating whether they are gram-positive or gram-negative.
[edit] Pathology
Because of Aermonas hydrophila’s structure, it is very toxic to many organisms. When it enters the body of its victim, it travels through the bloodstream to the first available organ. It has a gene called Aerolysin Cytotoxic Enterotoxin (ACT gene), that releases a toxin that can cause tissue damage. It is a most known as a pathogenic bacterium. Aeromonas hydrophila, Aeromonas caviae, and Aeromonas sobria are all considered to be “opportunistic pathogens,” meaning they would infect their victims at the first sign of exposure. Though Aeromonas hydrophila is known as a pathogenic bacterium, scientists have not been able to prove that it is the actual cause of some of the diseases it is associated with. It is believed that this bacterium aids in the infection of diseases, but do not cause the diseases themselves.
[edit] Occurence of exposure
Aeromonas hydrophila infections occur most during environmental changes, stressors, change in the temperature, in contaminated environments, and when an organism is already infected with a virus or another bacterium. It can also be ingested in the body by food products that have already been infected with the bacterium, such as seafood, meats, and even certain vegetables such as sprouts.
[edit] Fish and amphibians
Aeromonas hydrophila is associated with diseases mainly found in fish and amphibians, because these organisms live in aquatic environments. It is linked to a disease found in frogs called red leg, which causes internal and sometimes fatal hemorrhaging. When infected with Aeromonas hydrophila, fish are infected with diseases such as, ulcers, tail rot, fin rot, and haemorrhagic seticaemia. Haemorrhagic seticaemia causes lesions that lead to scale shedding, hemorrhaging in the gills and anal area, ulcers, exophthalmia, and abdominal swelling. Below is an image of ulcers found in on fish.
[edit] Human diseases
Aeromonas hydrophila is not as pathogenic to humans as it is to fish and amphibians. This bacterium is associated with diseases in humans. One of the diseases this Aeromonas hydrophila is associated with is gastroenteritis. This disease can infect anyone, but it occurs most in young children, people who have compromised immune systems and growth problems. This bacterium is linked to two types of gastroenteritis. The first type is a disease similar to cholera disease that features diarrhea. The other type of disease is dysenteric gastroenteritis, which causes loose stools to be filled with blood and mucus. The dysenteric gastroenteritis is the most severe out of the two types, and can last for weeks on end. Aeromonas hydrophila is also associated with Cellulitis, which is a skin infection that causes inflammation in the skin tissue. It also causes diseases such as myonecrosis and ecythma, which occurs most in organisms with compromised immune system.
[edit] Outbreaks
Though Aeromonas hydrophila causes serious diseases, there have never been serious outbreaks. There was an outbreak inside the intestinal tract of lizards in Puerto Rico. There were 116 different strains in all found in the lizards. On May 1, 1988 there was a small Aeromonas hydrophila outbreak in California. There were 225 isolates and 219 patients admitted in the hospital because of the bacterium. Confidential Morbidity Report cards were used to report the cases of the bacterium to the local health departments. Investigations were conducted, and reports were sent to the California department of health services for diagnosis and methods in treatment.
[edit] Treatments
Though Aeromonas hydrophila is very resistant to the common methods used to kill most bacteria, it can be eliminated. It can be killed using one percent sodium hypochlorite solution, and two percent calcium hypochlorite solution. It can be removed from the blood by using an agar medium containing sheep blood and the antibiotic ampicillin.
Chemotherapeutic agents such as chloramphenical, florenicol, tetracycline, sulphonamide, nitrofuran derivatives, and pyrodinecarboxylic acids are used to eliminate and control the infection of Aeromonas hydrophila. Terramycin is placed in fish food during hatchery operations as another chemotherapeutic agent in preventing Aeromonas hydrophila.
[edit] Preventing infection
It is ill advised to transfer fish from hatchery to hatchery without any sanitation. Hatchery workers should clean the fish, and check for bacterial infection between each operation. To avoid contamination oxygen levels in fish should be maintained, and fish should always be handled gently, to avoid injury. Prophylactic treatments can also be used when trying to prevent Aermonas hydrophila. These treatments include disinfectants, and Acriflavin.
[edit] References
- Fulton, MacDonald. "THE BACTERIUM AEROMONAS HYDROPHILA FROM LIZARDS OF THE GENUS ANOLIS IN PUERTO RICO". Lousiana State University Medical Center, New Orleans, LA. <www.uprm.edu/publications/cjs/VOL05/P099-102.PDF>. September 19, 2006
- Hayes, John. "Aeromonas hydrophila." Oregon State Univerisity. September 20, 2006. <http://hmsc.oregonstate.edu/classes/MB492/hydrophilahayes/>
- "Aeromonas hydrophila." Bad Bug Book Foodborne Pathogenic Microorganisms and Natural Toxins Handbook. September 20, 2006. <http://vm.cfsan.fda.gov/~mow/chap17.html>
- "Aeromonas hydrophila and Related Bacteria." International Specialty Supply. September 20, 2006. <http://www.sproutnet.com/Reports/aeromonas_hydrophila.htm>
- "Aeromonas hydrophila." September 20, 2006
<http://www.arrowscientific.com.au/Bacteria_aeromonas.html
- "Aeromonas." September 20, 2006 <http://www.microbewiki.kenyon.edu/index.php/Aeromonas>
