title: Mutants of Streptococcus suis types 1 and 2 impaired in expression of muramidase-released protein and extracellular protein induce disease in newborn germfree pigs.
abstract: The contribution of muramidase-released protein (MRP) and extracellular factor (EF) to the virulence of Streptococcus suis type 1 and 2 infections was studied. For that aim, we constructed mutants of S. suis types 1 and 2 by inactivating the genes encoding MRP and EF. Moreover, we changed a type 2 strain producing the 110-kDa EF protein into a strain producing a modified protein (EF*) of increased molecular mass. The chromosomally located mrp and epf genes were inactivated by replacement recombination by using nonreplicative plasmids. Newborn germfree pigs were inoculated with pathogenic type 1 and 2 strains and with the isogenic mutant strains. Wild-type as well as mutant strains induced fever, specific signs of disease, and lesions. Moreover, all mutant strains could be reisolated from the central nervous system of infected pigs. These results showed that inactivation or alteration of the mrp and epj genes had no measurable effect on the pathogenicity of S. suis types 1 and 2.
authors.affiliation: Department of Bacteriology, DLO Institute for Animal Science and Health, Lelystad, The Netherlands.
authors.forename: H E
authors.initials: HE
authors.lastname: Smith
authors.forename: U
authors.initials: U
authors.lastname: Vecht
authors.forename: H J
authors.initials: HJ
authors.lastname: Wisselink
authors.forename: N
authors.initials: N
authors.lastname: Stockhofe-Zurwieden
authors.forename: Y
authors.initials: Y
authors.lastname: Biermann
authors.forename: M A
authors.initials: MA
authors.lastname: Smits
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001426:Bacterial Proteins / Q000502:physiology*; D015153:Blotting, Western; D005856:Germ-Free Life; D009154:Mutation; D017011:Streptococcus suis / Q000472:pathogenicity*; D013552:Swine; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; C082316:Epf protein, Streptococcus suis