SURVIVAL POTENTIAL OF AEROMONAS-HYDROPHILA IN FRESH-WATERS AND NUTRIENT-POOR WATERS IN COMPARISON WITH OTHER BACTERIA

The survival of a genetically-marked Aeromonas hydrophila strain was s tudied in water microcosms using viable counts. Aeromonas hydrophila A WWX1 was shown to survive without decline in viable counts for at leas t 10 d in three of four filtered-autoclaved freshwaters (surface water and groundwater) and in all examined filtered-autoclaved nutrient-poo r waters (bottled spring water, Milli-Q and tap water), However, in th e unfiltered waters, a rapid decrease in viable counts of Aer. hydroph ila AWWX1 was observed after 1-5 d. The survival of Aer. hydrophila AW WX1 in nutrient-poor waters was compared with that of Pseudomonas fluo rescens P17 and Spirillum strain NOX. Survival characteristics were or ganism- and water-dependent. In the filtered-autoclaved waters, viable counts of Spirillum strain NOX were ca 1 log-unit higher than for Aer . hydrophila AWWX1 and Ps. fluorescens P17. The tested strains Aer. hy drophila AWWX1 and Ps. fluorescens P17 survived 3 to 20, respectively 2 to 4 times better in the filtered-autoclaved waters compared to the unfiltered waters. Apparently, any inherent capability of these micro- organisms to adapt to low-nutrient environments was undone by the pres ence of the autochthonous microbiota. The present findings that Aer. h ydrophila survives very poorly in several drinking waters is of utmost importance towards public health and arises questions: about the mech anisms involved.