Multiple major disease-associated clones of Legionella pneumophila have emerged recently and independently
- Sophia David1,
- Christophe Rusniok2,
- Massimo Mentasti3,
- Laura Gomez-Valero2,
- Simon R Harris4,
- Pierre Lechat2,
- John Lees4,
- Christophe Ginevra5,
- Philippe Glaser2,
- Laurence Ma2,
- Christiane Bouchier2,
- Anthony Underwood3,
- Sophie Jarraud5,
- Timothy G Harrison3,
- Julian Parkhill4 and
- Carmen Buchrieser2,6
- 1 Wellcome Trust Sanger Institute and Public Health England;
- 2 Institut Pasteur;
- 3 Public Health England;
- 4 Wellcome Trust Sanger Institute;
- 5 National Reference Centre for Legionella
- ↵* Corresponding author; email: cbuch{at}pasteur.fr
Abstract
Legionella pneumophila is an environmental bacterium and the leading cause of Legionnaires' disease. Just five sequence types (ST), from >2000 currently described, cause nearly half of disease cases in North West Europe. Here we report the sequence and analyses of 364 L. pneumophila genomes including 337 from the five disease-associated STs and 27 representative of the species diversity. Phylogenetic analyses revealed that the five STs have independent origins within a highly diverse species. The number of de novo mutations is extremely low with maximum pairwise single nucleotide polymorphisms (SNPs) ranging from 19 (ST47) to 127 (ST1), which suggests emergences within the last century. Isolates sampled geographically far apart differ by only a few SNPs, demonstrating rapid dissemination. These five STs have been recombining recently leading to a shared pool of allelic variants potentially contributing to their increased disease propensity. The oldest clone, ST1, has spread globally, and between 1940 and 2000, four new clones have emerged in Europe, which show long-distance, rapid dispersal. That a large proportion of clinical cases is caused by recently emerged and internationally dispersed clones, linked by convergent evolution, is surprising for an environmental bacterium traditionally considered to be an opportunistic pathogen. To simultaneously explain recent emergence, rapid spread and increased disease association, we hypothesize that these STs have adapted to new man-made environmental niches, which may be linked by human infection and transmission.
- Received May 8, 2016.
- Accepted September 16, 2016.
- Published by Cold Spring Harbor Laboratory Press
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