THE MGLB GENE, A POSSIBLE VIRULENCE DETERMINANT OF PORCINE BRACHYSPIRA SPECIES

摘要

The genus Brachyspira includes two important pathogens of pigs, Brachyspira hyodysenteriae and Brachyspira pilosicoli that cause swine dysentery and porcine colonic spirochaetosis respectively. B. innocens, B. intermedia, and B. murdochii are considered to be non-pathogenic. Identification of Brachyspira species is based on culture and phenotypic characterisation or molecular-based techniques (polymerase chain reaction [PCR] testing). Recently varying degrees of virulence have been detected within B.hyodysenteriae and atypical pathogenic Brachyspira species have been recognised. This has identified the need for new diagnostic techniques that are based on known virulence determinants. The objective of the current study was to determine within the porcine Brachyspira species, the prevalence of the putative virulence gene MglB that encodes the glucose-galactose lipoprotein. The MglB gene of Escherichia coli, aside from its function in high affinity transport of glucose-galactose., is a chemoreceptorin glucose and galatose chemotaxis. Chemotaxis towards mucin appears to be important in the mucosal localisation of B. hyodysenteriae and B. pilosicoli. Mucin is the principle constituent of the colonic mucus gel and consists of glycoproteins that can serve as a substrate for growth and chemotaxis of B. pilosicoli in-vitro. Galactosamine and glucosamine together make up half the pig colonic mucin glyocoproteins, and D-glucose, D-galactose, N-acetyl-D-glucosamine and D-glucosamine are utilised by B. pilosicoli as substrates for growth in-vitro. In a previous study an antigen of B. pilosicoli that was recognized by antibodies present in the sera of challenged-exposed pigs was characterised, and the encoding gene was identified. The predicted amino acid sequence had a high degree of similarity and identity to lipoproteins in the Mgl operon, specifically MglB. Surprisingly previous studies indicate MglB is present in B. pilosicoli but not present in B. hyodysenteriae.