ALTERATIONS IN TOTAL BACTERIA, IODONITROPHENYLTETRAZOLIUM (INT)-POSITIVE BACTERIA, AND HETEROTROPHIC PLATE COUNTS OF BOTTLED MINERAL-WATER

The quantitative variation in the microflora in bottled mineral waters stored in polyvinyl chloride bottles was studied immediately after bo ttling and after 7 days storage, over 9 months. The microflora was det ermined by combining total counts using ethidium bromide, and the numb er of iodonitrophenyltetrazolium (INT)-positive cells determined with heterotrophic plate counts on R(2)A for prolonged incubation periods a t 22 and 37 degrees C. Immediately after bottling of mineral water A, the total counts with ethidium bromide varied between 70.0 and 495.0 b acteria/mL. The number of INT-positive bacteria varied between 14.0 an d 40.0% counts. The heterotrophic plate counts were higher at 22 degre es C than at 37 degrees C and varied between 1.1 and 13.2% and between 0.7 and 9.3% of the total counts, respectively. After 7 days storage, total bacterial counts increased by 1000 times, indicating multiplica tion of bacteria that were present in low numbers immediately after bo ttling. The percentage of INT-positive bacteria remained between 2.6 a nd 39.0% of the total counts but the number of culturable bacteria was higher than the number of INT-positive cells. Similar counts were fou nd in other mineral waters (B, C, and D), but the numbers of INT-posit ive cells in two of them (B and D) were higher than the heterotrophic plate counts at 22 degrees C. These results show the presence in the a quifer and (or) bottling system of a flora that is neither INT-positiv e nor culturable and reinforce previous results that still mineral wat ers have a large bacterial population after storage.