The effect of preculture conditions on the culturability and viability of Aeromonas hydrophila when exposed to oligotrophic and cold stresses

The aim of this study is to assess the relationship between pre-culture conditions and loss of culturability of Aeromonas hydrophila exposed to a nutrient deprivation and low temperature (4°C). The present results show that the behavior of A. hydrophila, when exposed to nutritional deprivation and low temperature, depends on the pre-culture conditions. After a 60-days period of incubation in Filtered Sterilized Distilled Water (FSDW) at 4°C no culturable cells were observed for cells with a pre-culture in a liquid culture medium whereas a cell density of 1.8 log CFU/ml was observed for the bacterium with a pre-culture on solid medium with cells fixed on cellulose nitrate membrane. Colony count of A. hydrophila cells with anaerobic pre-culture declined to 0 CFU/ml within 16 days of incubation in FSDW at 4°C showing that the cells under these conditions are more sensitive to nutritional deprivation and low temperature than cells with a pre-culture under aerobic conditions. Our findings showed also no culturable cells, after 8 days of incubation in FSDW, for A. hydrophila with a pre-culture at 4°C. Moreover the present study showed no recovered cells from non culturable A. hydrophila when the FSDW was supplemented by catalase or sodium pyruvate. However, the addition of oxyrase, to non culturable A. hydrophila cells, was found to allow the recovery of non culturable cells.