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Paris, September 29, 2004
Press Release
LEGIONNAIRE¹S DISEASE: GENOMES OF THE Paris AND Lens STRAINS SEQUENCED
Legionellosis or Legionnaire¹s disease affected more than 1,000
people in France in 2003 and caused nearly 130 deaths. This emerging disease is
caused by Legionella pneumophila,
an environmental bacterium that can grow in hot water systems. A team at the
Institut Pasteur associated with the CNRS [French National Center for
Scientific Research] and in collaboration with the National Reference Center
for Legionella, Inserm [National Institute for Health and Medical Research] in
Lyon, compared the genome sequence of the strain responsible for an epidemic
that recently occurred near Lens (Nord-Pas-de-Calais region) with that of an
endemic strain frequently isolated in France. This work, published in Nature Genetics, may allow now to better understand how certain Legionella strains
are spread in the population by
aerosols originating from cooling towers. These results should also help to identify
new targets for the development of tools to fight these bacteria.
The
name Legionnaire¹s disease was coined due to an epidemic of legionellosis that
occurred in 1976 where Legionella pneumophila
affected 200 participants of the 58th American Legion Convention in
Philadelphia. Since then, many epidemics have been observed in North America
and Europe. An estimated 8,000 to 18,000 people die of Legionnaire¹s disease
each year in the United States. In France, although sporadic cases are
regularly reported throughout the country, eight particularly serious epidemics
originating from cooling towers have also occurred since 1998. Legionella are
parasites of amoebae present in fresh water and artificial water systems, but
are also able to cause disease in man, through respiratory passages, once they
are spread in the air via aerosols.
The team led by Carmen Buchrieser of the laboratory of Genomics of
Microbial Pathogens at Institut Pasteur, (directed by Frank Kunst and Philippe
Glaser) in association with the CNRS[1]
and in collaboration with the Génopole® Pasteur and the National Reference Center for Legionella (directed by
Jérôme Etienne[2]), sequenced
and compared the genomes of two Legionella
strains: one isolated from a nosocomial epidemic that had occurred at Hôpital
Georges Pompidou (Paris) in 2000 (named strain ³Paris²), and the other one responsible for a serious epidemic (86 cases and
17 deaths) that occurred in the North of France in winter 2003-2004 (named
strain ³Lens²). The researchers aimed to better
characterize the genetic basis of the virulence of Legionella pneumophila and to understand
differences occurring between these strains. Both belong to the same serogroup,
seropgroup 1, that is alone responsible for 84% of reported cases of
Legionnaire¹s disease.
Carmen Buchrieser and her colleagues have proven that Legionella pneumophila are subject to
significant genome variations, since about 13% differences were observed
between the two strains studied. They identified a large number of genes coding
proteins that might contribute to the adaptation of the bacteria to humans,
like proteins similar to those of superior organisms (amoebae to man), others
possessing domains probably capable of modifying the physiology of host cells,
which might be potential virulence factors. The identification of several
hundred genes that differ among the ³Paris²
and the ³Lens² strain together with its analysis should make it possible to
eventually understand what made certain strains particularly virulent and
enabled them to spread so dramatically through the population.
This work sheds light on the evolution of Legionella pneumophila over time and should make it possible to understand how this bacterium
is capable of adapting to hosts as different as amoebae (microorganisms living
in aqueous environments) and man. These new data also open new avenues to
create improved diagnostics as well as for the development of new, effective
therapeutic weapons and biocides for decontaminating water systems.
Sources:
Evidence in the Legionella pneumophila genome for
exploitation of host cell functions and high genome plasticity. Nature
Genetics, November 2004: vol 305, 1966-1968
Christel Cazalet* (1), Christophe Rusniok (1), Holger
Brüggemann, Nora Zidane (2),
Arnaud
Magnier (2), Laurence Ma (2), Magalie Tichit (2),
Sophie Jarraud (3), Christiane Bouchier (2), François Vandenesch (3), Frank
Kunst (1), Jerome Etienne (3), Philippe Glaser (1), and Carmen Buchrieser (1)
(1) Pathogenic
Microorganism Genomics Laboratory, CNRS URA 2171, Institut Pasteur
(2) Genomics
Platform, Pasteur Génopole Ile de France, Institut Pasteur
(3) National Legionella Reference Center, Bacteriology
Laboratory INSERM E-
0230, Faculty of Medecine, IFR 62, Lyon
*CNRS
Scholarship Veolia Water Anjou Recherche
________________________________________________________________
Contact
persons:
Institut
Pasteur - Press Office:
Nadine
Peyrolo, Bruno Baron
Tel:
+33 (0)1 44 38 33 30 - Email: bbaron@pasteur.fr
CNRS
- Press Office:
Isabelle
Tratner
Tel:
+33 (0)1 44 96 49 88 Email: isabelle.tratner@cnrs-dir.fr
INSERM
- Press Office:
Martine
Moëllic
Tel: +33 (0)1 44 23 60 97 Email: presse@tolbiac.inserm.fr