Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Identification and characterization of the cps locus of Streptococcus suis serotype 2: the capsule protects against phagocytosis and is an important virulence factor.

Abstract

A major part of the capsular polysaccharide biosynthesis (cps) locus of S. suis serotype 2 was cloned and characterized. Based on the established sequence, 14 open reading frames (ORFs), designated Orf2Z, Orf2Y, Orf2X, and Cps2A to Cps2K, were identified. 12 ORFs belonged to a single transcriptional unit. The gene products of 11 of these ORFs showed similarity to proteins involved in polysaccharide biosynthesis of other gram-positive microorganisms. Non-encapsulated isogenic mutants were generated in the cps2B and cps2EF genes by insertional mutagenesis. In contrast to the wild-type S. suis serotype 2 strain, the non-encapsulated strains were highly sensitive to ingestion by porcine alveolar lung macrophages in vitro. The non-encapsulated mutant strains were also avirulent in young germfree pigs after intranasal inoculation. It is concluded that the capsule of S. suis serotype 2 plays an essential role in pathogenesis.