title: High-throughput typing method to identify a non-outbreak-involved Legionella pneumophila strain colonizing the entire water supply system in the town of Rennes, France.
abstract: Two legionellosis outbreaks occurred in the city of Rennes, France, during the past decade, requiring in-depth monitoring of Legionella pneumophila in the water network and the cooling towers in the city. In order to characterize the resulting large collection of isolates, an automated low-cost typing method was developed. The multiplex capillary-based variable-number tandem repeat (VNTR) (multiple-locus VNTR analysis [MLVA]) assay requiring only one PCR amplification per isolate ensures a high level of discrimination and reduces hands-on and time requirements. In less than 2 days and using one 4-capillary apparatus, 217 environmental isolates collected between 2000 and 2009 and 5 clinical isolates obtained during outbreaks in 2000 and 2006 in Rennes were analyzed, and 15 different genotypes were identified. A large cluster of isolates with closely related genotypes and representing 77% of the population was composed exclusively of environmental isolates extracted from hot water supply systems. It was not responsible for the known Rennes epidemic cases, although strains showing a similar MLVA profile have regularly been involved in European outbreaks. The clinical isolates in Rennes had the same genotype as isolates contaminating a mall's cooling tower. This study further demonstrates that unknown environmental or genetic factors contribute to the pathogenicity of some strains. This work illustrates the potential of the high-throughput MLVA typing method to investigate the origin of legionellosis cases by allowing the systematic typing of any new isolate and inclusion of data in shared databases.
authors.affiliation: Université Paris-Sud, Institut de Génétique et Microbiologie, 91405 Orsay, France.
authors.forename: D
authors.initials: D
authors.lastname: Sobral
authors.forename: P
authors.initials: P
authors.lastname: Le Cann
authors.forename: A
authors.initials: A
authors.lastname: Gerard
authors.forename: S
authors.initials: S
authors.lastname: Jarraud
authors.forename: B
authors.initials: B
authors.lastname: Lebeau
authors.forename: F
authors.initials: F
authors.lastname: Loisy-Hamon
authors.forename: G
authors.initials: G
authors.lastname: Vergnaud
authors.forename: C
authors.initials: C
authors.lastname: Pourcel
mesh_terms: D001331:Automation / Q000379:methods; D016000:Cluster Analysis; D005602:France; D005838:Genotype; D057166:High-Throughput Screening Assays; D016952:Legionella pneumophila / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D018598:Minisatellite Repeats; D058889:Molecular Typing / Q000379:methods*; D016133:Polymerase Chain Reaction / Q000379:methods; D014871:Water Microbiology; D014881:Water Supply