Rapid detection of total and viable Legionella pneumophila in tap water by immunomagnetic separation, double fluorescent staining and flow cytometry.
Bottom Line: The recovery is over 85% of spiked Lp SG 1 cells in 1 l of tap water and detection limits are around 50 and 15 cells per litre for total and viable Lp, respectively.In 53% of the water samples from different taps and showers significantly higher concentrations of Lp were detected by flow cytometry.No correlation to the plate culture method was found.
Affiliation: Swiss Federal Institute for Aquatic Science and Technology (Eawag), Überlandstrasse 133, CH-8600, Dübendorf, Switzerland.Show MeSH
Mentions: A typical result obtained with environmental Lp cells in tap water is shown in Fig. 2. Results were acquired by plotting green fluorescence against both sideward scatter (Fig. 6A and B), blue fluorescence against sideward scatter (Fig. 6D and E), blue versus red fluorescence (Fig. 6F), and green versus blue fluorescence (Fig. 6C). The Lp clusters were gated in Fig. 6A, B, D and E by gates R1–4 and combined to a multigate G1, requiring a valid event to lie inside all 4 gates. In order to discriminate viable from dead cells the gate R5 was set in Fig. 6F as a red fluorescence threshold for PI‐negative cells. A box plot and polygonal gate was chosen for better visualization as compared with a histogram with a range gate. Thus, for viable Lp quantification, gate G1 and R5 were combined as Gate G2.
Affiliation: Swiss Federal Institute for Aquatic Science and Technology (Eawag), Überlandstrasse 133, CH-8600, Dübendorf, Switzerland.