Abstract

The aim of the study was to clarify if microbe enrichment cultures and monitoring of volatiles released by them could speed up the detection of indicator bacteria in water samples. The combination of Portable Microbe Enrichment Unit (PMEU) cultivation and ChemPro100i^® chemical detector were used to detect the hygiene indicating bacteria. When the water distribution network of Kuopio city was studied in early summer, more than 20 early warnings of heterotrophic bacterial growth were registered during one month from lake water and 9 sampling points in 350 km of tube lines compared to only one alarm of coliformic growth from the same samples when solely the Colilert^TM system was used. The results from the PMEU were used in repairs. After adding mixed cultures of Klebsiella and Escherichia coli strains to the tap water the first alarm of the microbe growth in the enrichment culture could be achieved in 4 to 8 h. The results obtained showed that the combination of the PMEU with ChemPro100i^®  could also be used in the detection of a single Salmonella cell from a millilitre of tap water after about 10 h enrichment in the selective Rappaport Vassiliadis Soy (RVS) broth. In conclusion, besides instantaneous enrichment of coliformic bacteria, also controlling total heterotrophic bacterial loads with option for pathogen screening is recommended for household water monitoring.

Key words: Water distribution, bacterial detection, Portable Microbe Enrichment Unit (PMEU), volatile sensing, Escherichia coli, Klebsiella, Salmonella, tap water, Rappaport Vassiliadis Soy (RVS) medium, Scentrion, Colilert.