title: The role of the capsule of the Streptococcus milleri group in its pathogenicity.
abstract: Study of the pathogenicity of encapsulated strains of the Streptococcus milleri group (SMG) was performed by examination of the ability to cause subcutaneous abscesses in mice and by phagocytosis and phagocytic killing of human polymorphonuclear neutrophils (PMNs) against the organisms. All 3 encapsulated isolates from patients with pneumonia or lung abscess induced abscesses in the mice; however, only 2 of 20 unencapsulated isolates from patients with lung abscess or thoracic empyema did so. The 3 encapsulated strains inhibited more phagocytosis and phagocytic killing of PMNs than the unencapsulated strains. In addition, encapsular material separated from Streptococcus constellatus RZYK001 also inhibited phagocytosis and phagocytic killing in proportion to increasing concentrations of the capsular material. These results suggest that capsular material produced by SMG might be a pathogenic factor.
authors.affiliation: Division of Internal Medicine, Department of Infectious Diseases Control, Graduate School and Faculty of Medicine, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, Japan. s-kanamori@par.odn.ne.jp
authors.forename: Shuzo
authors.initials: S
authors.lastname: Kanamori
authors.forename: Nobuchika
authors.initials: N
authors.lastname: Kusano
authors.forename: Takashi
authors.initials: T
authors.lastname: Shinzato
authors.forename: Atsushi
authors.initials: A
authors.lastname: Saito
mesh_terms: D000038:Abscess / Q000276:immunology / Q000382:microbiology*; D000818:Animals; D016667:Bacterial Capsules / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D009504:Neutrophils / Q000276:immunology; D010587:Phagocytosis; D013290:Streptococcal Infections / Q000276:immunology / Q000382:microbiology*; D034364:Streptococcus milleri Group / Q000472:pathogenicity*; D040521:Subcutaneous Tissue / Q000276:immunology / Q000382:microbiology*