Aeromonas hydrophila is a gram-negative, facultatively anaerobic, non-spore forming rod-shaped bacterium that is present in all freshwater environments and in estuarine environments. It is also found in a wide range of foods, including seafood products and shellfish, raw foods of animal origin (for example, poultry, ground meat, raw milk), and raw vegetables (Kirov 2003). Aeromonas spp. are ubiquitous and occur worldwide, but are most frequently isolated from treated and untreated water and animals associated with water such as fish and shellfish. Many authors use the name of A. hydrophila as a general term to include A. sobria and A. caviae as well as the main species of A. hydrophila (ICMSF 1996). In this document, A. hydrophila refers to this species only, unless otherwise indicated.
These bacteria are psychrotrophic and grow rapidly at refrigeration temperatures. Temperature range for growth is 2–45°C with an optimum range between 28C and 35C (ICMSF 1996). Growth is optimal in the presence of 1–2 per cent NaCl (aw = 0.991–0.986) and has been found to be inhibited completely at a NaCl concentration of 6.0 per cent (aw = 0.96) or pH 5.5. (ICMSF 1996).
