title: Regrowth of Legionella pneumophila in a heat-disinfected plumbing system.
abstract: We examined the factors involved in the occurrence of Legionellaceae in a hospital water system and the recontamination by Legionella pneumophila after a thermal disinfection procedure was studied. Three months after the heat treatment (70 degrees C), the regrowth of the two prevalent Legionella strains (L. pneumophila serogroup 1 [Oxford-like] and L. pneumophila serogroup 2) reached the original level of cell numbers. Genomic analysis (pulsed-field gel electrophoresis) revealed the strains to be survivors of the decontamination. Temperature tolerance experiments showed that the serogroup 1 strain exhibited a higher tolerance to 60 degrees C than the serogroup 2 strain, which could account for the order of reappearance of the strains after the heat treatment. Potential host amoebae, including Acanthamoeba spp. and Vahlkampfia spp., which are known to play a critical role in the amplification process of Legionella, were isolated from the plumbing system. In-vitro studies demonstrated both Legionella strains for a similar rate of multiplication in A. castellanii. In competitive coinfections, however, the serogroup 1 strain achieved a higher rate of multiplication if compared with the serogroup 2 strain.
authors.affiliation: Institut für Molekulare Infektionsbiologie, University of Würzburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Steinert
authors.forename: G
authors.initials: G
authors.lastname: Ockert
authors.forename: C
authors.initials: C
authors.lastname: Lück
authors.forename: J
authors.initials: J
authors.lastname: Hacker
mesh_terms: D000048:Acanthamoeba / Q000302:isolation & purification / Q000382:microbiology; D000656:Amoeba / Q000302:isolation & purification / Q000382:microbiology; D000818:Animals; D015169:Colony Count, Microbial; D004203:Disinfection / Q000379:methods*; D016521:Electrophoresis, Gel, Pulsed-Field; D006761:Hospitals; D006358:Hot Temperature; D016952:Legionella pneumophila / Q000145:classification / Q000254:growth & development* / Q000302:isolation & purification; D007877:Legionnaires' Disease / Q000517:prevention & control; D012703:Serotyping; D013696:Temperature; D014871:Water Microbiology; D014881:Water Supply