Dichelobacter nodosus

• Formerly known as Bacteroides
• Characteristics:
  • Large Gram negative rods with terminal swellings
  • Long polar fimbriae
  • 16 antigenic types of fimbriae - used to differentiate strains antigenically
  • All strains possess same O antigen
  • Colonies of virulent strains have a dark central zone, a pale granular middle zone and an irregular periphery
  • Strains detected by ELISA and PCR
  • Thermostable proteases and elastase contribute to pathogenesis
  • Keratinolytic proteases required for virulence
  • Fimbriae required for adhesion to hoof
  • Primary pathogen of epidermal tissues of hoof of ruminants, suriving briefly in the envionment
  • Passed from animal to animal
  • Causes foot rot in sheep along with other bacteria
• Ovine footrot:
  • Contagious, economically important disease
  • Wet pasture and hydrated stratum corneum leads to colonisation by Gram positive cocci and Arcanobacter pyogenes, followed by F. necrophorum; addition of D. nodosus causes footrot
  • Can lead to loss of hoof
• Immunity:
  • Homologous antibody to fimbrial antigen prevents adhesion and protects against footrot
  • Antibody must penetrate the epidermal layers and reach adequate concentration on the skin surface
  • Vaccine available