Diversity of Legionella pneumophila in cooling towers: Coculture kinetics and virulence studies

Sonia Ragull, Marian García-Núñez, María Luisa Pedro-Botet, Celestino Rey-Joly, Miquel Sabria

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Background: Legionella pneumophila (L. pneumophila) was isolated from three cooling towers involved in three community outbreaks of Legionnairesǐ disease. Each cooling tower had two different chromosomal DNA subtypes. However, only one matched identically to the clinical strains. To try to understand why only one of the environmental strains caused clinical cases we investigated the intrinsic virulence of these strains. Methods: We selected six strains of L. pneumophila sg.1: two strains (A1 and B1) from cooling tower 1, two strains (A2 and B2) from tower 2 and two strains (A3 and B3) from tower 3. One of the two subtypes (A) exhibited the same chromosomal DNA subtype as the strains isolated from the patients in each outbreak and the other exhibited a different subtype. The replication within macrophages, the presence of lipopolysaccharide epitope recognized by MAb 3/1 and the growth kinetics in BCYE broth were investigated. Isolates were typed by pulsed field electrophoresis. Results: The A strains did not have a higher virulence level, but were able to grow and survive better than strains B in BCYE broth. Conclusions: These results suggest that the strains better adapted to the environment will manage to displace the others and will be able to spread and infect humans. The adaptation to the environmental conditions could play an important role in the pathogenesis of the strains. © 2010 Elsevier España, S.L. All rights reserved.
Original languageEnglish
Pages (from-to)334-338
JournalEnfermedades Infecciosas y Microbiologia Clinica
Issue number5
Publication statusPublished - 1 May 2011


  • Community infections
  • Legionella pneumophila
  • Molecular epidemiology
  • Virulence traits


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