Population Genomics ofLegionella longbeachaeand Hidden Complexities of Infection Source Attribution

• DOI: 10.3201/eid2305.161165
• Publication Date: 2017-03-24T12:31:11Z
• Authors: Rodrigo Bacigalupe; Diane Lindsay; Giles Edwards; J. Ross Fitzgerald
• Keywords: Gene Flow; 0301 basic medicine; Infectious and parasitic diseases; RC109-216; phylogeny; Serogroup; 03 medical and health sciences; Legionella longbeachae; RNA, Ribosomal, 16S; Cluster Analysis; Humans; Phylogeny; Recombination, Genetic; Legionellosis; legionellosis; Research; R; Australia; Computational Biology; Genetic Variation; High-Throughput Nucleotide Sequencing; Genomics; United States; 3. Good health; RNA, Bacterial; Scotland; outbreaks; Medicine; legionella; epidemiology; Genome, Bacterial; New Zealand; Plasmids

Legionella longbeachae is the primary cause of legionellosis in Australasia and Southeast Asia and an emerging pathogen in Europe and the United States; however, our understanding of the population diversity of L. longbeachae from patient and environmental sources is limited. We analyzed the genomes of 64 L. longbeachae isolates, of which 29 were from a cluster of legionellosis cases linked to commercial growing media in Scotland in 2013 and 35 were non-outbreak-associated isolates from Scotland and other countries. We identified extensive genetic diversity across the L. longbeachae species, associated with intraspecies and interspecies gene flow, and a wide geographic distribution of closely related genotypes. Of note, we observed a highly diverse pool of L. longbeachae genotypes within compost samples that precluded the genetic establishment of an infection source. These data represent a view of the genomic diversity of L. longbeachae that will inform strategies for investigating future outbreaks.