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ABSTRACT: Legionella, the aetiological agent responsible for Legionellosis, is an opportunistic pathogen that infects humans upon the inhalation of contaminated aerosolized water droplets. Legionella is pleomorphic and its different morphotypes exhibit varying degrees of virulence. While the filamentous forms of Legionella pneumophila (Lp) have been reported in patient samples since the first description of legionellosis, their role in disease has not been studied. Our results show that both E-cadherin and β1 integrin receptors mediate filamentous Lp (FLp) attachment to lung epithelial cells (LECs). The activation of these receptors induces the formation of actin enriched membrane surface structures that we designated 'hooks' and 'membrane wraps'. These structures entrap the filaments on the cell surface leading to their gradual internalization through a zipper mechanism of phagocytosis dependent on actomyosin activity. The supply of E-cadherin receptors from the recycling pathway and β1 integrins released from focal adhesion turnover are required to sustain this process. Intracellular FLp inhabits a vacuolar compartment where filaments differentiate into short rods and replicate to produce infective progeny. Here we are reporting a first description of the invasion mechanism used by FLp to invade LECs. Therefore, filamentous morphotype of Lp can induce its own uptake by LECs and has the potential ability to cause disease.
Cellular Microbiology 06/2012; 14(10):1632-55. · 5.46 Impact Factor
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ABSTRACT: Legionellosis is mostly caused by Legionella pneumophila (Lp) and is defined by a severe respiratory illness with a case fatality rate ranging from 5 to 80%. In a previous study, we showed that a glycosaminoglycan (GAG)-binding adhesin of Lp, named Lcl, is produced during legionellosis and is unique to the L. pneumophila species. Importantly, a mutant depleted in Lcl (Δlpg2644) is impaired in adhesion to GAGs and epithelial cells and in biofilm formation. Here, we examine the molecular function(s) of Lcl and the transcriptional regulation of its encoding gene during different stages of the biofilm development. We show that the collagen repeats and the C-terminal domains of Lcl are crucial for the production of biofilm. We present evidence that Lcl is involved in the early step of surface attachment but also in intercellular interactions. Furthermore, we address the relationship between Lcl gene regulation during biofilm formation and quorum sensing (QS). In a static biofilm assay, we show that Lcl is differentially regulated during growth phases and biofilm formation. Moreover, we show that the transcriptional regulation of lpg2644, mediated by a prototype of QS signaling homoserine lactone (3OC12-HSL), may play a role during the biofilm development. Thus, transcriptional down-regulation of lpg2644 may facilitate the dispersion of Lp to reinitiate biofilm colonization on a distal surface.
PLoS ONE 01/2012; 7(9):e46462. · 4.09 Impact Factor
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ABSTRACT: Legionellosis is mostly caused by Legionella pneumophila and is defined by a severe respiratory illness with a case fatality rate ranging from 5 to 80%. In vitro and in vivo, interactions of L. pneumophila with lung epithelial cells are mediated by the sulfated glycosaminoglycans (GAGs) of the host extracellular matrix. In this study, we have identified several Legionella heparin binding proteins. We have shown that one of these proteins, designated Lcl, is a polymorphic adhesin of L. pneumophila that is produced during legionellosis. Homologues of Lcl are ubiquitous in L. pneumophila serogroups but are undetected in other Legionella species. Recombinant Lcl binds to GAGs, and a Δlpg2644 mutant demonstrated reduced binding to GAGs and human lung epithelial cells. Importantly, we showed that the Δlpg2644 strain is dramatically impaired in biofilm formation. These data delineate the role of Lcl in the GAG binding properties of L. pneumophila and provide molecular evidence regarding its role in L. pneumophila adherence and biofilm formation.
Infection and immunity 03/2011; 79(6):2168-81. · 4.21 Impact Factor
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Carla Duncan,
Jennifer L Guthrie,
Nathalie Tijet,
Naglaa Elgngihy,
Christine Turenne,
Christine Seah,
Rachel Lau,
Lisa McTaggart,
Gustavo Mallo,
Stephen Perusini,
Anu Rebbapragada,
Roberto Melano,
Donald E Low,
David Farrell,
Cyril Guyard
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ABSTRACT: During the early stages of the 2009/2010 swine-origin H1N1 influenza A (S-OIV H1N1 FluA) outbreak, the development and validation of sensitive and specific detection methods were a priority for rapid and accurate diagnosis. Between May and June 2009, 2 real-time reverse transcriptase-polymerase chain reaction (rRT-PCR) assays targeting the hemagglutinin and neuraminidase genes of the S-OIV H1N1 FluA virus were developed. These assays are highly specific, showing no cross-reactivity against a panel of respiratory viruses and can differentiate S-OIV H1N1 from seasonal FluA viruses. Analytical sensitivities of the 2 assays were found to be 10(-1) tissue culture infectious dose, 50%/ml. Clinical testing showed 99.2% sensitivity and 94.6-98.1% specificity. A large prospective analysis showed that 94.8-95.5% of S-OIV positive specimens were negative by seasonal H1/H3 subtyping. The large-scale validation data presented in this report indicate that these novel assays provide an accurate and efficient method for the rapid detection of S-OIV H1N1 FluA viruses.
Diagnostic microbiology and infectious disease 02/2011; 69(2):167-71. · 2.45 Impact Factor
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ABSTRACT: The water-borne pathogen Legionella pneumophila serogroup 1 (Lp1) is the most commonly reported etiologic agent of legionellosis. To examine the genetic diversity, the long-term epidemiology, and the molecular evolution of Lp1 clinical isolates, we conducted sequence-based typing on a collection of clinical isolates representing 3 decades of culture-confirmed legionellosis in Ontario, Canada. Analysis showed that the population of Lp1 in Ontario is highly diverse and combines lineages identified worldwide with local strains. Identical types were identified in sporadic and outbreak-associated strains. In the past 15 years, the incidence of some lineages distributed worldwide has tended to decrease, and local endemic clones and lineages have emerged. Comparative geographic distribution analysis suggests that some lineages are specific to eastern North America. These findings have general clinical implications for the study of Lp1 molecular evolution and for the identification of Lp1 circulating strains in North America.
Emerging Infectious Diseases 03/2010; 16(3):447-54. · 6.79 Impact Factor
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AliReza Eshaghi,
Joanne Blair,
Laura Burton,
Kam Wing Choi,
Cedric De Lima, Carla Duncan,
Cyril Guyard,
Rachel Higgins,
Ernesto Lombos,
Donald E Low,
Tony Mazzulli,
Steven J Drews
International journal of infectious diseases: IJID: official publication of the International Society for Infectious Diseases 11/2008; 13(3):e127-8. · 2.17 Impact Factor
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Jeff Powis,
Allison McGeer, Carla Duncan,
Ryan Goren,
Joyce C S de Azavedo,
Darrin J Bast,
Sylvia Pong-Porter,
Tony Mazzulli,
Karen Green,
Barbara Willey,
Donald E Low
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ABSTRACT: Fluoroquinolone susceptibility testing was performed on invasive group A streptococcus isolates from 1992-1993 and 2003 from Ontario, Canada. None were nonsusceptible to levofloxacin. Two of 153 (1.3%) from 1992-1993 and 7 of 160 (4.4%) from 2003 had a levofloxacin MIC of 2 mug/ml; all nine had parC mutations, and eight were serotype M6.
Antimicrobial Agents and Chemotherapy 06/2005; 49(5):2130-2. · 4.84 Impact Factor
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79:2168-2181.
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Carla Duncan,
Jennifer L. Guthrie,
Nathalie Tijet,
Naglaa Elgngihy,
Christine Turenne,
Christine Seah,
Rachel Lau,
Lisa McTaggart,
Gustavo Mallo,
Stephen Perusini,
Anu Rebbapragada,
Roberto Melano,
Donald E. Low,
David Farrell,
Cyril Guyard
69:167-171.
