Survival of Escherichia coli and Aeromonas hydrophila in non-carbonated mineral water.

The study was carried out on the survival of Escherichia coli and Aeromonas hydrophila in samples of mineral waters. Enumeration of the bacteria was performed by spread inoculation of samples (0.1 cm3) over the surface of selected media in Petri plates. Twenty bottles (four bottles of each of the five brands) of non-carbonated mineral waters with different levels of dissolved solids and organic content were chosen to study every strain. Ten bottles were stored at 4 degrees C, the other ten were kept at 22 degrees C. Half of the samples of mineral water was filtered, the remaining water was unfiltered. The resulting growth curves depended on the time of storage. The number of E. coli increased during the first two weeks (except the seventh day) and decreased during the next days. E. coli was detected in 70% of samples of water after 182 days. The number of A. hydrophila decreased during the first three days, increased on the seventh day and decreased during the next days. A. hydrophila was detected in 15% of the samples of water after 182 days. The temperature of storage was inessential for growth. The most important factors were the brand and the filtering or unfiltering of water. The highest numbers of the bacteria analysed were detected in filtered water, irrespective of the water brand and temperature of storage.