title: Legionella pneumophila strain associated with the first evidence of person-to-person transmission of Legionnaires' disease: a unique mosaic genetic backbone.
abstract: A first strong evidence of person-to-person transmission of Legionnaires' Disease (LD) was recently reported. Here, we characterize the genetic backbone of this case-related Legionella pneumophila strain ("PtVFX/2014"), which also caused a large outbreak of LD. PtVFX/2014 is phylogenetically divergent from the most worldwide studied outbreak-associated L. pneumophila subspecies pneumophila serogroup 1 strains. In fact, this strain is also from serogroup 1, but belongs to the L. pneumophila subspecies fraseri. Its genomic mosaic backbone reveals eight horizontally transferred regions encompassing genes, for instance, involved in lipopolysaccharide biosynthesis or encoding virulence-associated Dot/Icm type IVB secretion system (T4BSS) substrates. PtVFX/2014 also inherited a rare ~65 kb pathogenicity island carrying virulence factors and detoxifying enzymes believed to contribute to the emergence of best-fitted strains in water reservoirs and in human macrophages, as well as a inter-species transferred (from L. oakridgensis) ~37.5 kb genomic island (harboring a lvh/lvr T4ASS cluster) that had never been found intact within L. pneumophila species. PtVFX/2014 encodes another lvh/lvr cluster near to CRISPR-associated genes, which may boost L. pneumophila transition from an environmental bacterium to a human pathogen. Overall, this unique genomic make-up may impact PtVFX/2014 ability to adapt to diverse environments, and, ultimately, to be transmitted and cause human disease.
authors.affiliation: Bioinformatics Unit and Research Unit, National Institute of Health, Lisbon, Portugal.
authors.forename: Vítor
authors.initials: V
authors.lastname: Borges
authors.affiliation: Bioinformatics Unit and Research Unit, National Institute of Health, Lisbon, Portugal.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Nunes
authors.affiliation: Innovation and Technology Unit, National Institute of Health, Lisbon, Portugal.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Sampaio
authors.affiliation: Innovation and Technology Unit, National Institute of Health, Lisbon, Portugal.
authors.forename: Luís
authors.initials: L
authors.lastname: Vieira
authors.affiliation: Coordination of the Department of Infectious Diseases, National Institute of Health, Lisbon, Portugal.
authors.forename: Jorge
authors.initials: J
authors.lastname: Machado
authors.affiliation: National Reference Laboratory for Legionella, National Institute of Health, Lisbon, Portugal.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Simões
authors.affiliation: National Reference Laboratory for Legionella, National Institute of Health, Lisbon, Portugal.
authors.forename: Paulo
authors.initials: P
authors.lastname: Gonçalves
authors.affiliation: Bioinformatics Unit and Research Unit, National Institute of Health, Lisbon, Portugal.
authors.forename: João P
authors.initials: JP
authors.lastname: Gomes
mesh_terms: D016680:Genome, Bacterial; D044404:Genomic Islands; D006801:Humans; D016952:Legionella pneumophila / Q000235:genetics* / Q000472:pathogenicity; D007877:Legionnaires' Disease / Q000635:transmission*; D010802:Phylogeny; D011174:Portugal; D065288:Serogroup; D037521:Virulence Factors / Q000235:genetics; D000073336:Whole Genome Sequencing
chemical_list: D037521:Virulence Factors