Aeromonas hydrophila
Encyclopedia
Aeromonas hydrophila is a heterotrophic, Gram-negative
, rod shaped bacterium, mainly found in areas with a warm climate. 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 in the 1950s. This bacterium is the most well known of the six species of Aeromonas. It is also highly resistant to multiple medications, chlorine, and cold temperatures.
Cytotoxic Enterotoxin (ACT), a toxin that can cause tissue damage. Aeromonas hydrophila, Aeromonas caviae, and Aeromonas sobria are all considered to be opportunistic pathogens, meaning they rarely infect healthy individuals. Aeromonas hydrophila is widely considered a major fish and amphibian pathogen, and its pathogenicity in humans has been recognised for decades.
s, 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 through food products that have already been infected with the bacterium, such as seafood, meats, and even certain vegetables such as sprouts.
, and hemorrhagic septicaemia. Hemorrhagic septicaemia causes lesions that lead to scale shedding, hemorrhages in the gills and anal area, ulcers, exophthalmia, and abdominal swelling.
, which causes rice-water diarrhea. The other type of disease is dysenteric gastroenteritis, which causes loose stools
filled with blood and mucus. Dysenteric gastroenteritis is the most severe out of the two types, and can last for multiple weeks. Aeromonas hydrophila is also associated with cellulitis
, an infection that causes inflammation in the skin tissue. It also causes diseases such as myonecrosis and eczema in people with compromised immune systems.
solution.
Antibiotic
agents such as chloramphenicol
, florenicol, tetracycline, sulfonamide
, 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.
.
Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...
, rod shaped bacterium, mainly found in areas with a warm climate. This bacterium can also be found in fresh, salt, marine, estuarine, chlorinated, and un-chlorinated water. Aeromonas hydrophila can survive in aerobic and anaerobic
Hypoxia (environmental)
Hypoxia, or oxygen depletion, is a phenomenon that occurs in aquatic environments as dissolved oxygen becomes reduced in concentration to a point where it becomes detrimental to aquatic organisms living in the system...
environments. This bacterium can digest materials such as gelatin
Gelatin
Gelatin is a translucent, colorless, brittle , flavorless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar...
, and hemoglobin
Hemoglobin
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
. Aeromonas hydrophila was isolated from humans and animals in the 1950s. This bacterium is the most well known of the six species of Aeromonas. It is also highly resistant to multiple medications, chlorine, and cold temperatures.
Structure
Aeromonas hydrophila are Gram-negative straight rods with rounded ends (bacilli to coccibacilli shape) usually from .3 to 1 micrometer in width, and 1 to 3 micrometers in length. Aeromonas hydrophila does not form endospores, and can grow in temperatures as low as four degrees Celsius. These bacteria are motile by a polar flagella.Pathology
Because of Aeromonas 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 produces AerolysinAerolysin
In molecular biology, aerolysin is a cytolytic toxin exported by Aeromonas hydrophila, a Gram-negative bacterium associated with diarrhoeal diseases and deep wound infections. The mature toxin binds to eukaryotic cells and aggregates to form holes leading to the destruction of the membrane...
Cytotoxic Enterotoxin (ACT), a toxin that can cause tissue damage. Aeromonas hydrophila, Aeromonas caviae, and Aeromonas sobria are all considered to be opportunistic pathogens, meaning they rarely infect healthy individuals. Aeromonas hydrophila is widely considered a major fish and amphibian pathogen, and its pathogenicity in humans has been recognised for decades.
Pathogenic mechanism
It was believed that the pathogenicity of Aeromonas spp. is mediated by a number of extracellular proteins such as aerolysin, lipase, chitinase, amylase, gelatinase, hemolysins and enterotoxins. However the pathogenic mechanisms of Aeromonas spp. is remain unknown. The recently proposed type III secretion system (TTSS) mediated pathogenic mechanism has been proven to play a pivotal role in Aeromonas pathogenesis. The TTSS is specialized protein secretion machinery that export virulence factors delivered directly to host cells. These factors subvert normal host cell functions in ways that are beneficial to invading bacteria. In contrast to the general secretory pathway, type III secretion system is triggered when a pathogen comes in contact with host cells. ADP-ribosylation toxin is one of the effector molecules secreted by several pathogenic bacteria and translocated through TTSS and delivered into the host cytoplasm leads to interruption of NF-κB pathway, cytoskeletal damage and apoptosis. This toxin has been characterized in Aeromonas hydrophila (human diarrhoeal isolate), Aeromonas salmonicida (fish pathogen) and Aeromonas jandaei GV17, a pathogenic strain which can cause disease both in human and fish.Occurrence of exposure
Aeromonas hydrophila infections occur most during environmental changes, stressorStressor
Stressor is a chemical or biological agent, environmental condition, an external stimulus or an event that causes stress to an organism. An event that triggers the stress response may include for example:...
s, 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 through food products that have already been infected with the bacterium, such as seafood, meats, and even certain vegetables such as sprouts.
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, sometimes fatal hemorrhaging. When infected with Aeromonas hydrophila, fish develop ulcers, tail rot, fin rotFin rot
Fin rot is a symptom of disease or the actual disease in fish. This is a disease which is most often observed in aquaria and aquaculture, but can also occur in natural populations....
, and hemorrhagic septicaemia. Hemorrhagic septicaemia causes lesions that lead to scale shedding, hemorrhages in the gills and anal area, ulcers, exophthalmia, and abdominal swelling.
Human diseases
Aeromonas hydrophila is not as pathogenic to humans as it is to fish and amphibians. One of the diseases it can cause in humans is gastroenteritis. This disease can affect anyone, but it occurs most in young children and people who have compromised immune systems or growth problems. This bacterium is linked to two types of gastroenteritis. The first type is a disease similar to choleraCholera
Cholera is an infection of the small intestine that is caused by the bacterium Vibrio cholerae. The main symptoms are profuse watery diarrhea and vomiting. Transmission occurs primarily by drinking or eating water or food that has been contaminated by the diarrhea of an infected person or the feces...
, which causes rice-water diarrhea. The other type of disease is dysenteric gastroenteritis, which causes loose stools
Human feces
Human feces , also known as a stool, is the waste product of the human digestive system including bacteria. It varies significantly in appearance, according to the state of the digestive system, diet and general health....
filled with blood and mucus. Dysenteric gastroenteritis is the most severe out of the two types, and can last for multiple weeks. Aeromonas hydrophila is also associated with cellulitis
Cellulitis
Cellulitis is a diffuse inflammation of connective tissue with severe inflammation of dermal and subcutaneous layers of the skin. Cellulitis can be caused by normal skin flora or by exogenous bacteria, and often occurs where the skin has previously been broken: cracks in the skin, cuts, blisters,...
, an infection that causes inflammation in the skin tissue. It also causes diseases such as myonecrosis and eczema in people with compromised immune systems.
Outbreaks
Though Aeromonas hydrophila can cause 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 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.Treatments
Aeromonas hydrophila can be eliminated using one percent sodium hypochlorite solution and two percent calcium hypochloriteCalcium hypochlorite
Calcium hypochlorite is a chemical compound with formula 2. It is widely used for water treatment and as a bleaching agent...
solution.
Antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
agents such as chloramphenicol
Chloramphenicol
Chloramphenicol is a bacteriostatic antimicrobial that became available in 1949. It is considered a prototypical broad-spectrum antibiotic, alongside the tetracyclines, and as it is both cheap and easy to manufacture it is frequently found as a drug of choice in the third world.Chloramphenicol is...
, florenicol, tetracycline, sulfonamide
Sulfonamide (medicine)
Sulfonamide or sulphonamide is the basis of several groups of drugs. The original antibacterial sulfonamides are synthetic antimicrobial agents that contain the sulfonamide group. Some sulfonamides are also devoid of antibacterial activity, e.g., the anticonvulsant sultiame...
, 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.
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 AcriflavineAcriflavine
Acriflavine is a topical antiseptic. It has the form of an orange or brown powder. It may be harmful in the eyes or if inhaled. It is a dye and it stains the skin and may irritate. Commercial preparations are often mixtures with proflavine...
.