''Aeromonas dhakensis'' is a Gram-negative bacterium first isolated from aquariums in Portugal in 2005. The species is globally distributed in aquatic environments, like other species in the genus ''

Aeromonas ''Aeromonas'' is a genus of Gram-negative, facultative anaerobic, rod-shaped bacteria that morphologically resemble members of the family Enterobacteriaceae. Most of the 14 described species have been associated with human diseases. The most imp ...

''.

Isolation

''A. dhakensis'' was first isolated in 2005 from samples obtained from fish aquariums in Porto, Portugal and named ''A. aquariorum''. ''Aeromonas'' species are widely distributed in aquatic environments. Prior to the discovery of ''A. dhakensis'', the most prevalent species identified were '' A. hydrophila'', ''A. caviae'', and '' A. veronii''. Once identified, researchers found the species to be globally distributed in aquatic environments, similar to the other members of the genus. Due to its similarity to ''A. hydrophila'', ''A. dhakensis'' went unrecognized prior to 2005. The two species differ in that ''A. hydrophila'' is able to produce acid from L-arabinose, while ''A. dhakensis'' cannot. ''A. hydrophila'' is also less likely to use citrate as a carbon source than ''A. dhakensis''. Because of its similarity to other species of ''Aeromonas'', ''A. dhakensis'' was identified using DNA-DNA hybridization techniques, which identified the strains as a unique species of ''Aeromonas''. Researchers focused on ''rpoD'' and ''gyrB'' genes, which clearly identified the strains as a new species distinct from ''A. hydrophila''. In 2008, ''A. aquariorum'' was reclassified as ''A. dhakensis''. Phylogeny of Aeromonas

General characteristics

''A. dhakensis'' is a rod-shaped bacterium. Cells contain a single polar flagellum, so are motile. The organism tests positive for the ability to produce

catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting t ...

s and oxidases, and is capable of reducing

nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...

nitrite The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...

. The species is able to undergo both respiration and fermentation. Strains are able to grow on MacConkey agar with an optimal growth temperature of 30–37 °C. Strains of ''A. dhakensis'' that have been isolated are resistant to various beta-lactam antibiotics, including ampicillin, and other antibiotics such as

erythromycin Erythromycin is an antibiotic used for the treatment of a number of bacterial infections. This includes respiratory tract infections, skin infections, chlamydia infections, pelvic inflammatory disease, and syphilis. It may also be used duri ...

. Like its relative ''A. hydrophila'', ''A. dhakensis'' is an opportunistic pathogen, playing a role in gastrointestinal diseases, particularly

gastroenteritis Gastroenteritis, also known as infectious diarrhea and gastro, is an inflammation of the gastrointestinal tract including the stomach and intestine. Symptoms may include diarrhea, vomiting, and abdominal pain. Fever, lack of energy, and dehydra ...

. The species is also responsible for diseases in fish and amphibians. Treatment for an infection is the same as treatment for a ''A. hydrophila'' infection, with some antibiotics like tetracycline being effective against the pathogen.

Terramycin Oxytetracycline is a broad-spectrum tetracycline antibiotic, the second of the group to be discovered. Oxytetracycline works by interfering with the ability of bacteria to produce essential proteins. Without these proteins, the bacteria cannot ...

can be placed in aquatic environments to help prevent infections in fish by ''A. dhakensis''

References

{{Taxonbar, from=Q4688332 Aeromonadales