Search

Streptococcus suis causes meningitis and septicemia in pigs and is a zoonotic agent (1). In the Western hemisphere, human S. suis disease is infrequent and usually affects workers in the [...]

The capsular polysaccharide (CPS) of Streptococcus suis serotype 2 was isolated, purified, chemically modified, and characterized. Sugar and absolute configuration analyses of the CPS gave the following composition: D-Gal, 3; D-Glc, 1: D-GlcNAc, 1; D-Neu5Ac, 1: L-Rha, 1. Sialic acid was found to be terminal, and the CPS was quantitatively desialylated by mild acid hydrolysis. The CPS was also submitted to periodate oxidation followed by borohydride reduction and Smith degradation. Sugar and methylation analysis, ¹H and [sup.13]C nuclear magnetic resonance, and mass spectrometry of the native CPS or of its specifically modified products allowed to determine the repeating unit sequence: [4)[Neu5Ae(α2-6)Gal(β1-4)GlcNAc(β1-3)|Gal(β1-4) [Gal(α1-3)[Rha(β1-4)Glc(β1-].sub.n]. The backbone sequence was found to be identical to that of Streptococcus agaiactiae or group B Streptococcus (GBS) type VIII and Streptococcus pneumoniae type 23F. The S. suis CPS shares the sequence Neu5Ac-Gal-GlcNAc-Gal in common with GBS types Ia. Ib, II, III, and IV CPSs but differs from them by the presence of rhamnose and the fact that sialic acid is 2,6- rather than 2,3-linked to the following Gal. A correlation between the S. suis CPS sequence and genes of the serotype 2 cps locus encoding putative enzymes responsible for the biosynthesis of the repeating unit was tentatively established. Key words: chemical modification, nuclear magnetic resonance (NMR), mass spectrometry (MS), repeating unit sequence. On a isole, purifie, modifie chimiquemeni et caracterise le poly saccharide capsulaire (CPS) de Streptococcus suis serotype 2. Les analyses de sucres et de configuration absolue om donne la composition suivanle : D-Gal, 3; D-Glc, 1; D-GlcNAc, 1; D-Neu5Ac, 1; L-Rha, I. On a trouve que l'acide sialique etait terminal, et on a desialyle quantitativement le CPS par hydrolyse acide douce. On a egalement soumis le CPS a une oxydation au periodate suivie d'une reduction au borohydrare et a une degradation de Smith. Les analyses de sucres et par methylation, la resonance magnetique nucleaire du ¹H et du [sup.13]C et la spectrometrie de masse du CPS natif et de ses produits specifiquement modifies ont permis de determiner la sequence de l'unite repetitive : [4)[Neu5Ac(α2-6)Gal(β1-4)GlcNAc(β1- 3)]Gal(β1-4)[Gal(α1-3)][Rha(β1-4)Glc(β1-].sub.n]. On a trouve que la sequence du squelette etait identique a celle de Streptococcus agaiactiae ou Streptococcus du groupe B (GBS) type VIII et Streptococcus pneumoniae type 23F. Le CPS de S. suis partage la sequence Neu5Ac-Gal-GlcNAc-Gal en commun avec les CPS de GBS types la, lb, II, III et IV mais differe de ceux-ci par la presence de rhamnose et le fait que l'acide sialique est lie en 2,6 plutot qu'en 2,3 au Gal suivant. On a tente d'etablir une correlation entre la sequence du CPS de S. suis et les genes du locus cps du serotype 2 encodant des enzymes presumes responsables de la biosynthese de l'unite repetitive. Mots-des : modification chimique, resonance magnetique nucleaire (RMN), spectrometrie de masse, Introduction Streptococcus mis is the causative agent of meningitis, septicemia, arthritis, and sudden death in young pigs (Higgins and Gottschalk 2006). In addition, this pathogen is an emerging zoonotic agent [...]

Haemophilus parasuis, an important swine pathogen, is the aetiological agent of Glasser's disease. It is responsible for cases of polyserositis, meningitis and pneumonia in young pigs. To date, 15 serotypes have been described, although several non-typable isolates are frequently recovered from diseased animals. The pathogenesis of H. parasuis infection is poorly understood. To cause meningitis, H. parasuis would have to cross the blood-brain barrier (BBB), composed of brain microvascular endothelial cells (BMEC). The objective of this study was to investigate the ability of H. parasuis to interact with porcine brain microvascular endothelial cells (PBMEC). It was demonstrated that the serotype 5 reference strain of H. parasuis, Nagasaki (originally recovered from a case of meningitis), was able to adhere at very high levels to and, most importantly, invade PBMEC. These capacities were confirmed by electron microscopy. Actinobacillus pleuropnemoniae serotype 7 (strain WF 83), used as negative control, was not able to adhere to or invade PBMEC. Comparisons of the levels of adhesion and invasion by several H. parasuis field strains from different serotypes isolated from cases of either meningitis or pneumonia showed that isolates of serotypes 4 and 5 had a higher invasion capacity than isolates belonging to other serotypes. Inhibition studies demonstrated that PBMEC invasion by H. parasuis required rearrangement of actin microfilaments and microtubular cytoskeletal elements but not active bacterial DNA, RNA or protein synthesis. Characterization studies demonstrated that proteinaceous invasin(s) does not seem to play a major role in entry of H. parasuis into PBMEC. Intracellular viable H. parasuis were found in PBMEC up to 6 h after antibiotic treatment. Even at high bacterial doses, H. parasuis was not toxic to PBMEC. In swine, the invasion of endothelial cells of the BBB may play an important role in the pathogenesis of meningitis caused by H. parasuis.

Streptococcus serotype 2 adheres to epithelial cells through adhesins of the cell wall and causes cytotoxicity to epithelial cells of different cell lines through haemolysin. Results demonstrate that the bacterium follows a multistep infection process leading to bacteraemia and meningitis in pigs.

Affinity chromatography of the haemolysin toxin from Streptococcus suis type 2 using a thiopropyl Sepharose 6B column reveals that the extracellular protein has a molecular mass of 65 kDa. The haemolysin's response to oxygen and oxidizing agents, suppression by low levels of cholesterol, stimulation by reducing agents and transmembrane pore formation enable its classification into a family of antigenically related cholesterol-binding cytolytic toxins. S. suis haemolysin haemolytic activity is prevented by anti-streptolysin antibodies.