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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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PFGE pattern and SBT types of Lp1 isolates involved in the 2012 Québec City outbreak.
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pone-0103852-g001: PFGE pattern and SBT types of Lp1 isolates involved in the 2012 Québec City outbreak.

Mentions: Lp1 isolates recovered from 23 patients (n = 23 isolates) and from 32 (24%) cooling towers (n = 146 isolates) located in the vicinity of the outbreak discriminated into seven different PFGE profiles using SfiI (Figure 1). From the 23 Lp isolates obtained from humans, 22 displayed a unique PFGE cluster (pattern A). The strain from one patient with the different PFGE pattern (pattern B) represented a sporadic case unrelated to the outbreak. Among the 146 Lp1 isolates analysed from cooling towers, 6 different PFGE patterns (patterns A, C, D, F, G, H) were identified. Only one cooling tower system (two towers linked together) harbored strains with the same PFGE pattern (pattern A) as patients and it was identified as the source of the outbreak. The allelic profile of 53 isolates (23 patients and 30 environment isolates) with a minimum of one strain typed for each PFGE pattern was typed by SBT. The 53 isolates corresponded to 5 different sequence types (STs) (Figure 1). All patient isolates and isolates from the cooling tower with PFGE pattern A corresponded to ST-62. The patient with PFGE pattern B was ST-213. ST-1 was the most frequent type obtained from cooling towers (65%). ST-284 and ST-150 were found in 11% and 1.4% cooling towers isolates, respectively.


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)

PFGE pattern and SBT types of Lp1 isolates involved in the 2012 Québec City outbreak.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0103852-g001: PFGE pattern and SBT types of Lp1 isolates involved in the 2012 Québec City outbreak.
Mentions: Lp1 isolates recovered from 23 patients (n = 23 isolates) and from 32 (24%) cooling towers (n = 146 isolates) located in the vicinity of the outbreak discriminated into seven different PFGE profiles using SfiI (Figure 1). From the 23 Lp isolates obtained from humans, 22 displayed a unique PFGE cluster (pattern A). The strain from one patient with the different PFGE pattern (pattern B) represented a sporadic case unrelated to the outbreak. Among the 146 Lp1 isolates analysed from cooling towers, 6 different PFGE patterns (patterns A, C, D, F, G, H) were identified. Only one cooling tower system (two towers linked together) harbored strains with the same PFGE pattern (pattern A) as patients and it was identified as the source of the outbreak. The allelic profile of 53 isolates (23 patients and 30 environment isolates) with a minimum of one strain typed for each PFGE pattern was typed by SBT. The 53 isolates corresponded to 5 different sequence types (STs) (Figure 1). All patient isolates and isolates from the cooling tower with PFGE pattern A corresponded to ST-62. The patient with PFGE pattern B was ST-213. ST-1 was the most frequent type obtained from cooling towers (65%). ST-284 and ST-150 were found in 11% and 1.4% cooling towers isolates, respectively.

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