Unusual Legionnaires' outbreak in cool, dry Western Canada: an investigation using genomic epidemiology

Abstract

SUMMARYAn outbreak of Legionnaires' disease occurred in an inner city district in Calgary, Canada. This outbreak spanned a 3-week period in November–December 2012, and a total of eight cases were identified. Four of these cases were critically ill requiring intensive care admission but there was no associated mortality. All cases tested positive for Legionella pneumophila serogroup 1 (LP1) by urinary antigen testing. Five of the eight patients were culture positive for LP1 from respiratory specimens. These isolates were further identified as Knoxville monoclonal subtype and sequence subtype ST222. Whole-genome sequencing revealed that the isolates differed by no more than a single vertically acquired single nucleotide variant, supporting a single point-source outbreak. Hypothesis-based environmental investigation and sampling was conducted; however, a definitive source was not identified. Geomapping of case movements within the affected urban sector revealed a 1·0 km common area of potential exposure, which coincided with multiple active construction sites that used water spray to minimize transient dust. This community point-source Legionnaires' disease outbreak is unique due to its ST222 subtype and occurrence in a relatively dry and cold weather setting in Western Canada. This report suggests community outbreaks of Legionella should not be overlooked as a possibility during late autumn and winter months in the Northern Hemisphere.

Genome Sequencing Links Persistent Outbreak of Legionellosis in Sydney (New South Wales, Australia) to an Emerging Clone of Legionella pneumophila Sequence Type 211

“…Our findings indicate that cases among four temporally and/or spatially separate outbreaks of legionellosis that occurred in quick succession in metropolitan Sydney in 2016 were caused by a common clone of Lp1 ST211. The geographical distance between sites of potential exposure was much larger than previously recognized (Knox et al [19]), and this coupled with the temporal differences between these outbreaks led to the initial assumption that they were related to distinct exposures resulting from separate breaches of environmental health controls. However, phylogenetic analysis on both clinical and environmental isolates from these outbreaks by three independent genomic approaches confirmed that a single Lp1 clone was common to three of the four outbreaks.…”

Genome sequencing links persistent outbreak of legionellosis in Sydney to an emerging clone of Legionella pneumophila ST211

“…Our findings indicated that cases amongst four temporally and spatially separate outbreaks of legionellosis that occurred in quick succession in metropolitan Sydney in 2016 were caused by a common clone of Lp1 ST211. The geographical distance between sites of potential exposure was much larger than previously recognised (Knox et al, 2016) and this coupled with the temporal differences between these outbreaks led to the initial assumption that they were related to separate breaches of environmental health controls. However, phylogenetic analysis on both clinical and environmental isolates from these outbreaks by three independent genomic approaches confirmed that a common Lp1 clone was responsible across three of the four outbreaks.…”

“…The T4SS of Legionella are part of the dynamic accessory genome, known to contribute to fitness and virulence and play a crucial role in intracellular replication and survival (Khodr et al, 2016)(Rolando & Buchrieser, 2014; Schroeder et al, 2010; Voth et al, 2012). Unique T4ASS have been found in previous outbreak isolates (Graham et al, 2014) including from a recent outbreak in Western Canada, unique in its dry, cold conditions that were initially thought to be too harsh for survival of L. pneumophila (Knox et al, 2016). The element described in this study contained genes homologous to the Lvh region of other L. pneumophila strains and genes from this region are thought to assist in intracellular replication (Bandyopadhyay, Liu, Gabbai, Venitelli, & Steinman, 2007)(Bandyopadhyay, Lang, Rasaputra, & Steinman, 2013).…”

Water Management for Construction: Evidence for Risk Characterization in Community and Healthcare Settings: A Systematic Review

“…The present study found 54% of the events associated with construction activities occurred in fall and winter seasons, while 46% occurred in spring and summer months. For example, Knox et al [43] noted the anomaly of having a legionellosis outbreak during a sub-zero Canadian cold climate condition. Miragliotta et al [44] reported two construction workers contracted legionellosis while building an artesian well in Italy.…”

“…The present study found 697 (78%) disease cases and 83 (74%) deaths were associated with Legionella, spp. [16,[18][19][20][21][22][23]25,26,[29][30][31][32][35][36][37][38][39][40][41][42][43][44][45][46]. Other opportunistic waterborne pathogens such as NTM and Sphingomonas, spp.…”