The occurrence of Aeromonas species in drinking water supplies of an area of the Dolomite Mountains, Italy.

A study was made of the occurrence of Aeromonas spp. in drinking water supplies in a mountain area in northeast Italy (the Dolomites). On account of its location, the water in question is exposed to a low level of pollution and systematic chemical disinfection is not necessary. Out of 7395 water samples analysed over a 3 year period, 1623 (21 x 95%) were found to be positive for Aeromonas, with levels ranging from 1 to 240 cfu 100 ml-1; 72 x 4% of the strains were identified as Aer. hydrophila, 14 x 7% as Aer. caviae and 12 x 9% as Aer. sobria. The percentage of recovery from surface water (approximately 40%) was found to be higher than that of ground water (springs: 24 x 9%; wells : 28x 6%). Aeromonas spp. were isolated from 21 x 7% of samples from the distribution network and showed no significant variations compared with water from reservoirs. There was no evidence, therefore, of after-growth in the distribution system. No correlation was found between the concentration of Aeromonas spp. and faecal indicator organisms. As the distribution of Aeromonas spp. was unrelated to anthropic pollution, it is believed that the search for these micro-organisms should be adopted as a further indicator of drinking water quality, especially in waters such as those in the present investigation not undergoing systematic purification treatment.