Aeromonas dhakensis

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 dhakensis
Scientific classification
Domain: Bacteria
Phylum: Pseudomonadota
Class: Gammaproteobacteria
Order: Aeromonadales
Family: Aeromonadaceae
Genus: Aeromonas
Species:
A. dhakensis
Binomial name
Aeromonas dhakensis
(Huys et al. 2002) Beaz-Hidalgo et al. 2015
Synonyms

Aeromonas aquariorum

Isolation

A. dhakensis was first isolated in 2005 from samples obtained from fish aquariums in Porto, Portugal and named A. aquariorum.[1] 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.[2] In 2008, A. aquariorum was reclassified as A. dhakensis.[3]

Phylogenetic tree showing the relationship of A. dhakensis to other members of the Aeromonas based on gyrB and rpoD gene sequences

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 catalases and oxidases, and is capable of reducing nitrate to nitrite . 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.

Like its relative A. hydrophila, A. dhakensis is an opportunistic pathogen, playing a role in gastrointestinal diseases, particularly gastroenteritis.[4] 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 can be placed in aquatic environments to help prevent infections in fish by A. dhakensis

References
  1. Martinez-Murcia, A.J. "Aeromonas aquariorum sp. nov., isolated from aquaria of ornamental fish" International Journal of Systematic and Evolutionary Biology. 2012
  2. Aravena-Roman, Max, et al. "Aeromonas aquariorum Is Widely Distributed in Clinical and Environmental Specimens and Can Be Misidentified as Aeromonas hydrophila" Journal of Clinical Microbiology.2011. http://jcm.asm.org/content/49/8/3006.long
  3. Beaz-Hidalgo, Roxana; Martínez-Murcia, Antonio; Figueras, Maria José (2013). "Reclassification of Aeromonas hydrophila subsp. Dhakensis Huys et al. 2002 and Aeromonas aquariorum Martínez-Murcia et al. 2008 as Aeromonas dhakensis sp. nov. Comb nov. And emendation of the species Aeromonas hydrophila". Systematic and Applied Microbiology. 36 (3): 171. doi:10.1016/j.syapm.2012.12.007. PMID 23485124.
  4. Ottaviani D, Parlani C, Masini L, Leoni F, Canonico C, Sabatini L, Bruscolini F, Pianetti A (2011). "Putative virulence properties of Aeromonas strains isolated from food, environmental and clinical sources in Italy: A comparative study". International Journal of Food Microbiology. 144 (3): 538–545. doi:10.1016/j.ijfoodmicro.2010.11.020. PMID 21138783.
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