Possible virulence factors of Aeromonas spp. from food and water.

Thirty-one isolates of Aeromonas spp. from food and water in Norway were classified and tested for possible virulence factors including cytotoxins (tissue cultures, PCR), enterotoxins (PCR) and invasion ability (Caco-2 cells). Five different species were recorded, A. caviae (9/31), A. hydrophila (15/31), A. schubertii (3/31), A. trota (3/31) and A. veronii biovar veronii (1/31). One of the A. hydrophila strains was probably responsible for a small outbreak of food poisoning caused by ingestion of raw fermented fish. All the A. hydrophila strains produced and secreted cytotoxins at 37 degrees C, as well as two A. trota strains and the single A. veronii biovar veronii strain. In some cases increased cytotoxin secretion was observed under osmotic stress. The majority of the A. caviae strains which produced cytotoxins at 30 degrees C were unable to produce and/or secrete cytotoxins at 37 degrees C. One A. schubertii strain and one A. caviae strain were invasive.