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Chapter 106 : Legionella Detection from Water Samples by Real-Time PCR
This chapter deals about the direct detection of Legionella from hospital water samples by commercial real-time (RT)-PCR system, that offers rapid results and reduced risk of cross-contamination. The preliminary results of 61 water samples from 6 hospitals and 15 water samples from air conditioning systems are presented and compared with those of the isolation method. Water samples were concentrated by filtration through cellulose acetate membrane filter and resuspended in 10 ml of the same water. The principle steps were cell lysis with proteinase K, purification on spin column and elution. Culture was positive in 28 (45.9%) hospital water samples, and the strains were identified as Legionella pneumophila serogroup 1, 3, 6, and 2-14 and Legionella spp. The results of qualitative RT-PCR were as follows: Legionella spp. was positive (detection limit: 133 GU/liter) in 60 (98.4%) samples and L. pneumophila was positive in 44 (72.1%). The results of culture and qualitative analysis for L. pneumophila by RT-PCR are shown. All hospitals examined showed some positive samples for culture and PCR, except for one that was culture negative and PCR positive. All water samples from air conditioning systems were culture negative, but RT-PCR was positive in 15 water samples for Legionella spp. and in 2 for L. pneumophila. In conclusion, Legionella detection by RT-PCR from environmental methods seems to be promising. However, at the moment, correlation between the method-result interpretations and public health significance need further evaluations.