Introduction of Aeromonas hydrophila
Table of Contents
Aeromonas hydrophila is a gram-negative, facultative anaerobe, rod-shaped motile(due to single polar flagellum) bacterium without capsule and spore having a size from 0.3-1.0 µm wide by 1.0-3.5 µm long. It is generally found in the aquatic environment. Its presence can not be ignored in drinking water, wastewater, sewage, and food. It is an emerging pathogen responsible for numerous clinical conditions. e.g. gastroenteritis, skin infections, peritonitis, bacteremia, meningitis, cholera-like illness, hemolytic uremic syndrome (HUS), and necrotizing fasciitis.
Biochemical Reactions of Aeromonas hydrophila
| Basic Features | Properties |
| 1. Gram Staining | Gram-Negative Rods (GNRs) |
| 2. Spore | Non-Sporing |
| 3. Capsule | Negative |
| 4. Motility | Motile |
| 5. Pigment | Tan to buff-color |
| 6. Growth in potassium cyanide (KCN) medium | Positive |
| 7. Catalase test | Positive |
| 8. Oxidase test | Positive |
| 9. Nitrate reduction test | Positive |
| 10. MR (Methyl Red) test | Positive |
| 11. VP (Voges- Proskauer) assay | Positive |
| 12. OF (Oxidative-Fermentative) test | Positive |
| 13. Gas | Positive (mostly) |
| 14. H2S production | Positive |
| 15. Indole formation | Positive |
| 16. Urease/ urea hydrolysis test | Negative |
| 17. Citrate/citrate utilization | Positive |
| 18. DNase test | Positive |
| 19. Glucose fermentation | Positive |
| 20. Maltose fermentation | Positive |
| 21. Lactose fermentation | Variable |
| 22. Sucrose fermentation | Positive |
| 23. Xylose fermentation | Negative |
| 24. Mannitol fermentation | Positive |
| 25. Acetate Utilization | Positive |
| 26. ONPG (β-galactosidase) | Positive |
| 27. Phenylalanine Deaminase (PDA)/PPA Test | Negative |
| 28. Gelatin Hydrolysis | Positive |
| 29. Esculin Hydrolysis test | Positive (mostly) |
| 30. Lysine Decarboxylase Test | Positive |
| 31. Ornithine Decarboxylase Test | Negative |
| 32. Arginine Dihydrolase Test | Positive |
| 33. Gelatin Hydrolysis/Liquefaction | Positive |
| 34. Maximum Growth Temperature | 41°C |
| 35. Hemolysis on blood agar | Positive |
Keynotes on Aeromonas
- Aeromonas hydrophila complex is a group of genera A. hydrophila A. bestiarum and A. salmonicida.
- It is an emerging pathogen.
- Aeromonas species grow at a range of temperatures from 0 to 42ºC.
- Common pathogenic species of Aeromonas are A. hydrophila, Aeromonas veronii, and Aeromonas schubertii.
- They possess many extracellular enzymes like proteases, lipases, nucleases, sulphatases, lecithinase, chitinase, amylase, and stapholysin.
Aeromonas Pictures
Aeromonas hydrophila beta-hemolytic colony on blood agar
Aeromonas hydrophila growth on MacConkey agar
Aeromonas in Hanging Drop Preparation
Aeromonas hydrophila colony characteristics on CLED agar
Further Readings
- https://www.researchgate.net/figure/biochemical-tests-of-A-hydrophila-isolates_tbl1_316660080
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4601520/
- https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/aeromonas-hydrophila
- https://catalog.hardydiagnostics.com/cp_prod/Content/hugo/Aeromonas.htm
- Al-shalah. L. AM, The study characters of Aeromonas hydrophila on some media. Mesop. environ. j., 2017, Special Issue A.;121-129.
- https://www.researchgate.net/figure/Biochemical-properties-of-Aeromonas-hydrophila_tbl1_231614040
- Garrity, George Brenner, Don J., Krieg, Noel R., Staley, James R. (2005). Bergey’s Manual of Systematic Bacteriology. Volume 2: The Proteobacteria, Part B: The Gammaproteobacteria.
- Sharon L. Abbott, Wendy K. W. Cheung, J. Michael Janda. The Genus Aeromonas: Biochemical Characteristics, Atypical Reactions, and Phenotypic Identification Schemes Journal of Clinical Microbiology Jun 2003, 41 (6) 2348-2357; DOI: 10.1128/JCM.41.6.2348-2357.2003
- https://www.uptodate.com/contents/aeromonas-infections