Molecular analyses of drinking water bacteria critical for human health issues: Distinction between live and dead species and high resolution in situ detection of pathogenic bacteria exemplified for Legionella pneumophila

Abstract

The transmission of pathogens by drinking water can pose a significant health risk to the consumer. Today’s tools to assess hygienic quality and potential health risks of drinking water are still mostly cultivation based. The drawbacks of these methods (e.g. bacteria that enter a viable but nonculturable state) confirm the need for new detection tools in drinking water surveillance. Molecular tools that are based on the analysis of nucleic acids (DNA and RNA) can therefore help to detect and quantify microbial pathogens in drinking water and to analyze all bacteria in a given drinking water sample. In this study, molecular and cellular tools have been used to assess the community structure and viability of the drinking water microflora of a small scale drinking water distribution system located in Braunschweig, Germany. The developed approach enabled monitoring of the bacterial drinking water community and assessment of the physiological state of taxonomic groups of interest. Applied on a time to time basis, the approach can therefore contribute to the development of a more efficient and safer drinking water treatment. Species of the genus Legionella are ubiquitous in many natural freshwater environments. Epidemiological analyses of infections caused by L. pneumophila depend on the accurate identification of strains, preferably at the clonal level. Available genotyping methods (like MLST and MLVA) require a prior isolation of L. pneumophila from the environmental or clinical sample. In this study, the approved MLVA-8 typing scheme for L. pneumophila was adapted to environmental DNA for a fast and accurate typing of L. pneumophila isolates in one environmental samples without the need for cultivation based methods. Both developed approaches allow a better assessment of risks associated with bacteria in drinking water critical for human health and support its improved processing and management.