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Chapter 33 : Persistence and Genotypic Stability of Legionella in a Potable-Water System in a Hotel over a 20-Month Period
Category: Bacterial Pathogenesis
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This chapter determines the prevalence of Legionella spp. and identifies the chromosomal DNA subtypes and the genomic stability of these isolates during a 20-month follow-up period in the potable-water distribution system of a hotel. From June 2003 to March 2005, 110 water samples were collected from a hotel water supply comprising 11 sample collections of water. Legionella pneumophila serogroup (sg.) 1 was isolated in 49 (44.55%) of the 110 samples tested. The cold water distal point was L. pneumophila–positive throughout the whole study period. It should be pointed out that this distal point of cold water was an infrequently used point (roof-top tap) with stagnant water, which may explain the low chlorine levels (range, 0.05 to 0.95 mg of Cl2 per liter), the heating of water during warmer seasons and thus, colonization by Legionella throughout the study period. Environmental isolates of Legionella were genotypically characterized by pulsed-field gel electrophoresis. The number of colonized points was uniform throughout the 20-month study. All L. pneumophila isolates analyzed showed the same chomosomal DNA genotype, which indicated the clone stability over the 20-month follow-up period.
Pulsed-field gel electrophoresis. M, Market; 1, point 1 (June 2003); 2, point 2 (October 2003); 3, point 3 (January 2004); 4, point 4 (June 2004); 5, point 5 (June 2003);6, point 6 (October 2003); 7, point 7 (January 2004); 8, point 8 (June 2004);9, point 9 (March 2005); 10, point 4 (March 2005); 11, point 11 (March 2005).
Positive distal points of the hot potable distribution system on each collection round
Isolates typed by Sfi I pulsed field gel electrophoresis (PFGE)