title: Colony types and virulence traits of Legionella feeleii determined by exopolysaccharide materials.
abstract: Legionella feeleii is a Gram-negative pathogenic bacterium that causes Pontiac fever and pneumonia in humans. When L. feeleii serogroup 1 (ATCC 35072) was cultured on BCYE agar plates, two types of colonies were observed and exhibited differences in color, opacity and morphology. Since the two colony types are white rugose and brown translucent, they were termed as white rugose L. feeleii (WRLf) and brown translucent L. feeleii (BTLf), respectively. They exhibited different growth capacities in BYE broth in vitro, and it was found that WRLf could transform to BTLf. Under the electron microscope, it was observed that WRLf secreted materials which could be stained with ruthenium red, which was absent in BTLf. When U937 macrophages and HeLa cells were infected with the bacteria, WRLf manifested stronger internalization ability than BTLf. Intracellular growth in murine macrophages and Acanthamoeba cells was affected by the level of initial phagocytosis. WRLf was more resistant to human serum bactericidal action than BTLf. After being inoculated to guinea pigs, both organisms caused fever in the animals. These results suggest that ruthenium red-stained materials secreted in the surroundings may play a crucial role in determining L. feeleii colony morphology and virulence traits.
authors.affiliation: Department of Bacteriology, Graduate school of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan 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 Microbiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan.
authors.forename: Midori
authors.initials: M
authors.lastname: Ogawa
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; D006168:Guinea Pigs; D006367:HeLa Cells; D006801:Humans; D007875:Legionella / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism / Q000472:pathogenicity*; D007876:Legionellosis / Q000382:microbiology*; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D008854:Microscopy, Electron; D010587:Phagocytosis; D010641:Phenotype; D011135:Polysaccharides, Bacterial / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D012430:Ruthenium Red; D020298:U937 Cells; D014774:Virulence
chemical_list: D011135:Polysaccharides, Bacterial; D012430:Ruthenium Red
keywords: Legionella feeleii; Pontiac fever; brown translucent colony; colony transformation; exopolysaccharide; white rugose colony