title: Comparative analysis of virulence traits between a Legionella feeleii strain implicated in Pontiac fever and a strain that caused Legionnaires' disease.
abstract: Legionella strains of the same species and serogroup are known to cause Legionnaires' disease (a potentially fatal atypical pneumonia) or Pontiac fever (a mild, flu-like disease), but the bacterial factors that define these dramatic differences in pathology have not been elucidated. To gain a better understanding of these factors, we compared the characteristics of Legionella feeleii strains that were isolated from either a sample of freshwater implicated in an outbreak of Pontiac fever (ATCC 35072, serogroup 1, LfPF), or a patient with Legionnaires' disease (ATCC 38549, serogroup 2, LfLD). Growth of LfPF and LfLD in BYE broth was slower than the positive control, Legionella pneumophila strain JR32. However, LfLD grew faster than LfPF at 42 °C. After in vitro infection to J774 murine or U937 human macrophage cell lines and A549 human lung epithelial cell line, LfLD showed a higher cell infection rate, stronger internalization by host cells, and greater cytotoxicity than that of LfPF. Large amounts of IL-6 and IL-8 were secreted by human host cells after infection with LfLD, but not with LfPF. LfLD possessed mono-polar flagellum while LfPF was unflagellated. When LfLD was cultured at 25, 30 and 37 °C, the bacteria had higher motility rate at lower temperatures. Based on our results, this is the first study that showed distinct characteristics between LfPF and LfLD, which may give important leads in elucidating differences in their virulence.
authors.affiliation: Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan. Electronic address: wcl1986@bact.med.kyushu-u.ac.jp.
authors.forename: Changle
authors.initials: C
authors.lastname: Wang
authors.affiliation: Department of Microbiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan.
authors.forename: Mitsumasa
authors.initials: M
authors.lastname: Saito
authors.affiliation: Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Tamami
authors.initials: T
authors.lastname: Tanaka
authors.affiliation: Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Kazunobu
authors.initials: K
authors.lastname: Amako
authors.affiliation: Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Yoshida
mesh_terms: D000818:Animals; D058491:Bacterial Load; D001431:Bacteriological Techniques; D002460:Cell Line; D003470:Culture Media; D016207:Cytokines / Q000378:metabolism; D004847:Epithelial Cells / Q000276:immunology / Q000382:microbiology; D014644:Genetic Variation; D006801:Humans; D007875:Legionella / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification* / Q000502:physiology; D007876:Legionellosis / Q000382:microbiology* / Q000473:pathology*; D008124:Locomotion; D008264:Macrophages / Q000276:immunology / Q000382:microbiology; D051379:Mice; D013696:Temperature; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics*
chemical_list: D003470:Culture Media; D016207:Cytokines; D037521:Virulence Factors
keywords: Bacterial infection; Host cell immune response; Legionella feeleii; Legionnaires' disease; Pontiac fever