title: Loss of capsule among Streptococcus suis isolates from porcine endocarditis and its biological significance.
abstract: Streptococcus suis, particularly serotype 2, is a pathogen of both pigs and humans associated with a wide range of diseases, including meningitis, septicaemia and endocarditis. Among the genes in the capsular polysaccharide biosynthesis (cps) locus, cps2J exists only in the serotype 2 and 1/2 strains; therefore, cps2J-positive strains are suspected to have capsules of serotype 2 or 1/2. Coagglutination using antiserotype 1 and antiserotype 2 sera and/or transmission electron microscopy analysis of 288 cps2J-positive isolates from pigs showed that 32 (100 %) isolates from meningitis were encapsulated, whereas 86 (34 %) of 256 isolates from endocarditis were unencapsulated, indicating that capsule loss often occurred in the isolates from endocarditis. To investigate the genetic backgrounds, we randomly selected 43 unencapsulated isolates and analysed their cps loci by PCR scanning. Among them, 8 and 10 isolates apparently had deletions and insertions, respectively, in cps loci. In addition, a representative unencapsulated isolate and an unencapsulated strain showed adherence to porcine and human platelets, a major virulence determinant for infective endocarditis, to a significantly greater extent than the encapsulated strains. Although the capsule is considered to be an important virulence factor in S. suis, these results suggest that loss of capsular production is beneficial to S. suis in the course of infective endocarditis.
authors.affiliation: Research Center for Food Safety, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan.
authors.forename: Nattakan
authors.initials: N
authors.lastname: Lakkitjaroen
authors.affiliation: United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan.|Research Division of Bacterial and Parasitic Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-0856, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Takamatsu
authors.affiliation: Research Division of Bacterial and Parasitic Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-0856, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Okura
authors.affiliation: Epidemiological Information Section, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-0856, Japan.
authors.forename: Masumi
authors.initials: M
authors.lastname: Sato
authors.affiliation: Research Division of Bacterial and Parasitic Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-0856, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Osaki
authors.affiliation: Research Center for Food Safety, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Sekizaki
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000235:genetics / Q000276:immunology* / Q000648:ultrastructure; D001483:Base Sequence; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004696:Endocarditis / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D007564:Japan; D046529:Microscopy, Electron, Transmission / Q000662:veterinary; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012189:Retrospective Studies; D017422:Sequence Analysis, DNA; D012703:Serotyping / Q000662:veterinary; D013290:Streptococcal Infections / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D017011:Streptococcus suis / Q000235:genetics / Q000276:immunology* / Q000648:ultrastructure; D013552:Swine; D013553:Swine Diseases / Q000276:immunology / Q000382:microbiology*; D015047:Zoonoses / Q000382:microbiology*
chemical_list: D004269:DNA, Bacterial