Molecular typing of a Legionella pneumophila outbreak in Ontario, Canada

Gilmour, Matthew W.; Bernard, Kathryn; Tracz, Dobryan M.; Olson, Adam B.; Corbett, Cindi R.; Burdz, Tamara; Ng, Betty; Wiebe, Deborah; Broukhanski, George; Boleszczuk, Peter; Tang, Patrick; Jamieson, Frances; Domselaar, Gary Van; Plummer, Francis A.; Berry, Jody D.

doi:10.1099/jmm.0.46738-0

Cited by 45 publications

(40 citation statements)

References 16 publications

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“…1A and C). Importantly, ST222 was also the cause of one of the biggest LD outbreaks in North America that took place in Ontario, Canada, in the fall of 2005 and caused 112 illnesses and 23 deaths (39). This suggests that the strains within clonal complex C may indeed have higher virulence potential.…”

Section: Discussionmentioning

confidence: 99%

Prevalence of Sequence Types among Clinical and Environmental Isolates of Legionella pneumophila Serogroup 1 in the United States from 1982 to 2012

et al. 2014

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cSince the establishment of sequence-based typing as the gold standard for DNA-based typing of Legionella pneumophila, the Legionella laboratory at the Centers for Disease Control and Prevention (CDC) has conducted routine sequence-based typing (SBT) analysis of all incoming L. pneumophila serogroup 1 (Lp1) isolates to identify potential links between cases and to better understand genetic diversity and clonal expansion among L. pneumophila bacteria. Retrospective genotyping of Lp1 isolates from sporadic cases and Legionnaires' disease (LD) outbreaks deposited into the CDC reference collection since 1982 has been completed. For this study, we compared the distribution of sequence types (STs) among Lp1 isolates implicated in 26 outbreaks in the United States, 571 clinical isolates from sporadic cases of LD in the United States, and 149 environmental isolates with no known association with LD. The Lp1 isolates under study had been deposited into our collection between 1982 and 2012. We identified 17 outbreak-associated STs, 153 sporadic STs, and 49 environmental STs. We observed that Lp1 STs from outbreaks and sporadic cases are more similar to each other than either group is to environmental STs. The most frequent ST for both sporadic and environmental isolates was ST1, accounting for 25% and 49% of the total number of isolates, respectively. The STs shared by both outbreak-associated and sporadic Lp1 included ST1, ST35, ST36, ST37, and ST222. The STs most commonly found in sporadic and outbreak-associated Lp1 populations may have an increased ability to cause disease and thus may require special attention when detected.

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Section: Discussionmentioning

confidence: 99%

Prevalence of Sequence Types among Clinical and Environmental Isolates of Legionella pneumophila Serogroup 1 in the United States from 1982 to 2012

et al. 2014

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“…Alternatively, changing target genes due to too high variability in nucleic acids for the flaA gene could be another way to increase SBT or NPSBT performance. This method can also be improved by using additional genes other than those already chosen, as has been previously tried (15). The detection limit of each gene amplification has not been determined, as it is most likely strain specific; indeed, several strain-dependent polymorphisms exist in the sequences targeted by the primers, resulting in mismatches during amplification and making the detection limit vary from one strain to another.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of a Nested-PCR-Derived Sequence-Based Typing Method Applied Directly to Respiratory Samples from Patients with Legionnaires' Disease

et al. 2009

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“…Data were obtained from L. pneumophila isolates from the following sources: (i) the EU Legionella culture collection (Fry et al, 1999(Fry et al, , 2000(Fry et al, , 2002Gaia et al, 2003Gaia et al, , 2005 , 2006; Coscollá & González-Candelas, 2007;Fendukly et al, 2007;Gilmour et al, 2007;Ratzow et al, 2007;Wong et al, 2006). Only data from isolates considered epidemiologically unrelated to any other, or those subsequently shown to be unrelated to the index case isolate in each cluster, were included.…”

Section: Methodsmentioning

confidence: 99%

Clonal population structure of Legionella pneumophila inferred from allelic profiling

Edwards

Fry²,

Harrison³

2008

Microbiology

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The population structure of Legionella pneumophila was investigated by analysing nucleotide sequences from six loci (flaA, pilE, asd, mip, mompS and proA) of 335 globally distributed isolates from clinical and environmental sources over a 29-year period (1977-2006). Data were obtained from unrelated isolates from Europe (n5270), Japan (n531), Canada (n57), the USA (n524) and Australia (n51). The country of origin of two strains was unknown. Analysis of these isolates indicated significant linkage disequilibrium between the six loci. Application of six sequence-based recombination detection tests did not reveal evidence of recombination, but estimates of rates of recombination and mutation made by a seventh test suggested that recombination could have occurred at a rate similar to, but probably lower than, that of mutation.Genealogies inferred under models with and without recombination were congruent with each other, providing no definitive evidence regarding recombination, and were in agreement with sequence clusters identified by graph methods. Further evidence supporting the distinct nature of two of the three subspecies of L. pneumophila, subsp. fraseri and subsp. pascullei, was also found. The ratios of non-synonymous to synonymous nucleotide polymorphisms for each of the allele sets were examined and revealed that the putative virulence loci mompS and pilE are under diversifying pressure, while the allelic regions of three other loci linked to virulence (flaA, proA and mip) do not appear to be. INTRODUCTIONFollowing the recognition of the aetiological agent of Legionnaires' disease in 1977(McDade et al., 1977, phenotypic and genotypic analyses of Legionella pneumophila have mainly focused on the short-term epidemiology of the bacterium. In this scenario, the aim has been to demonstrate potential environmental sources of infection, thereby allowing timely intervention, in order to prevent further infection. Many such methods have been developed and applied with the purpose of discriminating between epidemiologically unrelated strains of L. pneumophila, particularly those belonging to serogroup (sg) 1 (Edelstein et al., 1986;Fry et al., 1999; Saunders et al., 1990;Schoonmaker et al., 1992;van Ketel et al., 1984).The utility of the multi-locus sequence typing (MLST) approach, in which sequences from five to 10 housekeeping genes are determined, in the identification of major bacterial lineages associated with invasive disease was first described in 1998 (Enright & Spratt, 1998;Maiden et al., 1998). Since then, this robust and portable technique (or variations of it) has been applied to the study of genetic diversity and clonal expansion, and to the long-term epidemiological analysis of microbial populations (see http://pubmlst.org/ and http://www.mlst.net/) (Giske et al., 2006;Paraskevopoulos et al., 2006;Vassileva et al., 2006).Recently, a similar approach, termed sequence-based typing (SBT), developed by members of the European Working Group for Legionella Infections (EWGLI), was applied to the epidemiolo...

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Molecular typing of a Legionella pneumophila outbreak in Ontario, Canada

Cited by 45 publications

References 16 publications

Prevalence of Sequence Types among Clinical and Environmental Isolates of Legionella pneumophila Serogroup 1 in the United States from 1982 to 2012

Prevalence of Sequence Types among Clinical and Environmental Isolates of Legionella pneumophila Serogroup 1 in the United States from 1982 to 2012

Evaluation of a Nested-PCR-Derived Sequence-Based Typing Method Applied Directly to Respiratory Samples from Patients with Legionnaires' Disease

Clonal population structure of Legionella pneumophila inferred from allelic profiling

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