Bacterial flora in bottled uncarbonated mineral drinking water

Abstract

A quantitative study of bacterial populations in mineral water was carried out. Samples were stored at 6 and 20 °C, and the colony counts were determined on tryptone agar plates incubated at 22 and 37 °C. Samples were collected from the spring source in sterile glass flasks and from the bottling factory in conventional plastic and glass containers. In both cases, the initial population (101–102 cfu/mL water) increased to 105–106 cfu/mL after 3 days storage as determined from plate counts incubated at 22 °C. The levels reached by this population were similar to those of samples of mineral water obtained at the market stage. Results from plate counts incubated at 37 °C showed that populations in samples collected at the bottling factory reached 102–103 cfu/mL. No growth was observed in water collected from spring source. Bacterial multiplication was not stopped even when water was stored at 6 °C. Caulobacter was the genus found most frequently in both types of samples, followed by Sphaerotilus-Leptothrix. Acinetobacter calcoaceticus and Pseudomonas fluorescens were frequently found in only two springs, and Pseudomonas putida, Arthrobacter, Aeromonas hydrophila, and Corynebacterium were isolated less frequently. Janthinobacterium was recovered only once from a single spring. A giant bacterium closely resembling Hyphomicrobium and a budding one similar to Pasteuria were recovered from all samples of a single spring and from some of the commercial samples.