Limits...
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.

Show MeSH

Related in: MedlinePlus

Phylogenic tree of Legionella pneumophila strains.There are 4 groups: outbreak related (O), contemporary (C), environmental (E) and 1996 strains (1996). The samples marked with a star symbol are from the cooling tower that was the source of the outbreak. The samples marked with a dot symbol are from patient unrelated to the outbreak of 2012. There is an average of 0.01 base substitution per site overall and an average of 0.0003 base substitution per site for the patient group.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4126679&req=5

pone-0103852-g002: Phylogenic tree of Legionella pneumophila strains.There are 4 groups: outbreak related (O), contemporary (C), environmental (E) and 1996 strains (1996). The samples marked with a star symbol are from the cooling tower that was the source of the outbreak. The samples marked with a dot symbol are from patient unrelated to the outbreak of 2012. There is an average of 0.01 base substitution per site overall and an average of 0.0003 base substitution per site for the patient group.

Mentions: We sequenced with the Illumina technology the genome of 23 Lp isolates from patients related to the outbreak, 4 isolates from contemporary patients not related to the outbreak, 8 isolates from cooling towers and 5 Lp isolates gathered during the 1996 Quebec City outbreak. Isolates from cooling towers were chosen to represent each environmental PFGE patterns. Whole genome phylogeny of these sequences and reference Lp genomes were constructed (Figure 2). This phylogeny was constructed based on an alignment of all the contigs of every strain and 6 reference sequences. All outbreak patient strains clustered together in the phylogenetic tree, showing that they are closely related. One of the sampled environmental sites clustered with the patient isolates, indicating that it was the source of the outbreak. Our data showed that the Québec City outbreak strains differed from strains observed in other major outbreaks such as the Philadelphia, Paris, Lens, Corby and Alcoy strains (Table 1 and Figure 2).


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)

Phylogenic tree of Legionella pneumophila strains.There are 4 groups: outbreak related (O), contemporary (C), environmental (E) and 1996 strains (1996). The samples marked with a star symbol are from the cooling tower that was the source of the outbreak. The samples marked with a dot symbol are from patient unrelated to the outbreak of 2012. There is an average of 0.01 base substitution per site overall and an average of 0.0003 base substitution per site for the patient group.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0103852-g002: Phylogenic tree of Legionella pneumophila strains.There are 4 groups: outbreak related (O), contemporary (C), environmental (E) and 1996 strains (1996). The samples marked with a star symbol are from the cooling tower that was the source of the outbreak. The samples marked with a dot symbol are from patient unrelated to the outbreak of 2012. There is an average of 0.01 base substitution per site overall and an average of 0.0003 base substitution per site for the patient group.
Mentions: We sequenced with the Illumina technology the genome of 23 Lp isolates from patients related to the outbreak, 4 isolates from contemporary patients not related to the outbreak, 8 isolates from cooling towers and 5 Lp isolates gathered during the 1996 Quebec City outbreak. Isolates from cooling towers were chosen to represent each environmental PFGE patterns. Whole genome phylogeny of these sequences and reference Lp genomes were constructed (Figure 2). This phylogeny was constructed based on an alignment of all the contigs of every strain and 6 reference sequences. All outbreak patient strains clustered together in the phylogenetic tree, showing that they are closely related. One of the sampled environmental sites clustered with the patient isolates, indicating that it was the source of the outbreak. Our data showed that the Québec City outbreak strains differed from strains observed in other major outbreaks such as the Philadelphia, Paris, Lens, Corby and Alcoy strains (Table 1 and Figure 2).

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