[Experiences with optimized methods for the detection of legionellae in drinking water]

Entry of Legionellae into domestic water systems by passing through the drinking water distribution network has been assumed. To prove this question, samples were collected within a two years period at warm and cold water taps of households, the pipeline network and three water works of the city of Mainz, and examined for the presence of Legionellae. To detect even very small numbers of Legionellae, improvement of the conventional isolation procedure was necessary. Additionally, large volumes of cold water samples (50-250 L) were processed by using a pressure filter. For identification of Legionellae, an immunological rapid test (colony-blot-assay, own development) and a commercial gene-probe test (EnvironAmp Legionella Kits, Applied Biosystems) were enclosed in the programme. With the refined techniques the detection limit was improved while expenses of time and labour were reduced. Finally, the advantages and disadvantages of the single methods are discussed. For routine detection of Legionellae in the microbiological laboratory, a combination of effective methods is proposed which are easy to perform.