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Genomic characterization of a large outbreak of Legionella pneumophila serogroup 1 strains in Quebec City, 2012.

Lévesque S, Plante PL, Mendis N, Cantin P, Marchand G, Charest H, Raymond F, Huot C, Goupil-Sormany I, Desbiens F, Faucher SP, Corbeil J, Tremblay C - PLoS ONE (2014)

Bottom Line: Two new Legionellaceae plasmids were found only in the epidemic strain.The LVH type IV secretion system was found in the 2012 outbreak isolates but not in the ones from the 1996 outbreak and only in half of the contemporary human isolates.At least four Icm/Dot effectors in the epidemic strains were absent in the environmental strains suggesting that some effectors could impact the intracellular replication in human macrophages.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Santé Publique du Québec (LSPQ)/Institut National de Santé Publique du Québec, Québec, Canada.

ABSTRACT
During the summer of 2012, a major Legionella pneumophila serogroup 1 outbreak occurred in Quebec City, Canada, which caused 182 declared cases of Legionnaire's disease and included 13 fatalities. Legionella pneumophila serogroup 1 isolates from 23 patients as well as from 32 cooling towers located in the vicinity of the outbreak were recovered for analysis. In addition, 6 isolates from the 1996 Quebec City outbreak and 4 isolates from patients unrelated to both outbreaks were added to allow comparison. We characterized the isolates using pulsed-field gel electrophoresis, sequence-based typing, and whole genome sequencing. The comparison of patients-isolated strains to cooling tower isolates allowed the identification of the tower that was the source of the outbreak. Legionella pneumophila strain Quebec 2012 was identified as a ST-62 by sequence-based typing methodology. Two new Legionellaceae plasmids were found only in the epidemic strain. The LVH type IV secretion system was found in the 2012 outbreak isolates but not in the ones from the 1996 outbreak and only in half of the contemporary human isolates. The epidemic strains replicated more efficiently and were more cytotoxic to human macrophages than the environmental strains tested. At least four Icm/Dot effectors in the epidemic strains were absent in the environmental strains suggesting that some effectors could impact the intracellular replication in human macrophages. Sequence-based typing and pulsed-field gel electrophoresis combined with whole genome sequencing allowed the identification and the analysis of the causative strain including its likely environmental source.

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Related in: MedlinePlus

Mapping of the legionellosis cases around the outbreak source.Ninety six percent (96%) of the cases were within 3 km (area 1) of the cooling tower responsible for the outbreak (identified by the black dot). The remaining cases were within 11 km of the outbreak source (area 2).
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pone-0103852-g005: Mapping of the legionellosis cases around the outbreak source.Ninety six percent (96%) of the cases were within 3 km (area 1) of the cooling tower responsible for the outbreak (identified by the black dot). The remaining cases were within 11 km of the outbreak source (area 2).

Mentions: We report on one of the largest North American outbreaks of LD of the last decades. This outbreak had 182 confirmed cases including 13 fatalities. The LD cases diagnosed spanned a large geographical area, however 96% of the cases were within a 3 km range (Figure 5). Several of the sampled cooling towers contained Lp1. Ultimately the source of the epidemic was traced to a single cooling tower. The epidemiological typing scheme of the Quebec City outbreak (ST-62) was already described in North America and Europe according to the SBT international database. In Canada, ST-62 had been identified in Ontario, Nova-Scotia and on one occasion in Quebec City in 1998 [23], [24]. ST-213 was identified for one patient considered a sporadic case. This type is rarely reported and is restricted to North America according to the SBT database. Among Lp1 isolates found in the environment, ST-1 was the predominant genotype. ST-1 is one of the most frequent types reported in the SBT database. It was also frequently observed from environment strains in Ontario [24]. This clone is probably well-adapted to environment survival or host infection [24]–[26]. The two other types obtained from the environment, ST-150 and ST-264 are also rare. The first one has been reported from environment in China and Japan, and the second in the USA.


Genomic characterization of a large outbreak of Legionella pneumophila serogroup 1 strains in Quebec City, 2012.

Lévesque S, Plante PL, Mendis N, Cantin P, Marchand G, Charest H, Raymond F, Huot C, Goupil-Sormany I, Desbiens F, Faucher SP, Corbeil J, Tremblay C - PLoS ONE (2014)

Mapping of the legionellosis cases around the outbreak source.Ninety six percent (96%) of the cases were within 3 km (area 1) of the cooling tower responsible for the outbreak (identified by the black dot). The remaining cases were within 11 km of the outbreak source (area 2).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126679&req=5

pone-0103852-g005: Mapping of the legionellosis cases around the outbreak source.Ninety six percent (96%) of the cases were within 3 km (area 1) of the cooling tower responsible for the outbreak (identified by the black dot). The remaining cases were within 11 km of the outbreak source (area 2).
Mentions: We report on one of the largest North American outbreaks of LD of the last decades. This outbreak had 182 confirmed cases including 13 fatalities. The LD cases diagnosed spanned a large geographical area, however 96% of the cases were within a 3 km range (Figure 5). Several of the sampled cooling towers contained Lp1. Ultimately the source of the epidemic was traced to a single cooling tower. The epidemiological typing scheme of the Quebec City outbreak (ST-62) was already described in North America and Europe according to the SBT international database. In Canada, ST-62 had been identified in Ontario, Nova-Scotia and on one occasion in Quebec City in 1998 [23], [24]. ST-213 was identified for one patient considered a sporadic case. This type is rarely reported and is restricted to North America according to the SBT database. Among Lp1 isolates found in the environment, ST-1 was the predominant genotype. ST-1 is one of the most frequent types reported in the SBT database. It was also frequently observed from environment strains in Ontario [24]. This clone is probably well-adapted to environment survival or host infection [24]–[26]. The two other types obtained from the environment, ST-150 and ST-264 are also rare. The first one has been reported from environment in China and Japan, and the second in the USA.

Bottom Line: Two new Legionellaceae plasmids were found only in the epidemic strain.The LVH type IV secretion system was found in the 2012 outbreak isolates but not in the ones from the 1996 outbreak and only in half of the contemporary human isolates.At least four Icm/Dot effectors in the epidemic strains were absent in the environmental strains suggesting that some effectors could impact the intracellular replication in human macrophages.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Santé Publique du Québec (LSPQ)/Institut National de Santé Publique du Québec, Québec, Canada.

ABSTRACT
During the summer of 2012, a major Legionella pneumophila serogroup 1 outbreak occurred in Quebec City, Canada, which caused 182 declared cases of Legionnaire's disease and included 13 fatalities. Legionella pneumophila serogroup 1 isolates from 23 patients as well as from 32 cooling towers located in the vicinity of the outbreak were recovered for analysis. In addition, 6 isolates from the 1996 Quebec City outbreak and 4 isolates from patients unrelated to both outbreaks were added to allow comparison. We characterized the isolates using pulsed-field gel electrophoresis, sequence-based typing, and whole genome sequencing. The comparison of patients-isolated strains to cooling tower isolates allowed the identification of the tower that was the source of the outbreak. Legionella pneumophila strain Quebec 2012 was identified as a ST-62 by sequence-based typing methodology. Two new Legionellaceae plasmids were found only in the epidemic strain. The LVH type IV secretion system was found in the 2012 outbreak isolates but not in the ones from the 1996 outbreak and only in half of the contemporary human isolates. The epidemic strains replicated more efficiently and were more cytotoxic to human macrophages than the environmental strains tested. At least four Icm/Dot effectors in the epidemic strains were absent in the environmental strains suggesting that some effectors could impact the intracellular replication in human macrophages. Sequence-based typing and pulsed-field gel electrophoresis combined with whole genome sequencing allowed the identification and the analysis of the causative strain including its likely environmental source.

Show MeSH
Related in: MedlinePlus