Abstract

The microbial contamination in a spring water distribution system in the Western Cape, South Africa was investigated. Sampling at various points from the spring and throughout the bottling system started in February and continued until November 2004. The number of culturable cells was determined using the heterotrophic plate count (HPC) and total microbial counts were evaluated by flow cytometric analysis (FCM). Heterotrophic plate counts in the final bottled water ranged from 1.34 x 10⁸ cfu/ml (week 1) to 5 x 10⁴ cfu/ml (week 46). In comparison, the total cell counts (FCM) ranged from 2.09 x 10⁸microorganisms/ml (week 1) to 5.70 x 10⁷ microorganisms/ml (week 46).The higher FCM counts indicated that the flow cytometry technique was able to detect viable but non-culturable organisms in the water and was thus more reliable for the routine quantitative enumeration of microbial populations in water samples. 16S ribosomal ribonucleic acid (rRNA) of the bacterial species present was amplified with PCR and phylogenetic trees were constructed using the neighbour-joining algorithm.  The sequenced isolates from the various water samples belonged to the major groups Bacillus sp, and Enterobacteriaceaeand included Shigella boydii, Serratia sp., Enterobacter asburiae and Pseudomonas sp.

Key words: Bacterial contamination, flow cytometry, heterotrophic plate count, molecular typing, spring water distribution system.