Toxins and pathogenesis

TOXINS AND PATHOGENESIS

Toxins

  • B. nodosus causing foot rot produces keratinolytic enzymes in greater amounts.
  • F. necrophorum produces an exotoxin (leukotoxin) and necrotizing endotoxin.
  • The endotoxin when inoculated intradermally into rabbit causes necrosis.
  • The exotoxin when inoculated in skin of rabbits causes mild erythema but when administerd intravenously causes maciation or death of rabbits in a few hours.

Pathogenesis

  • The infections are often endogenous, arising from nor­mal flora at the site or by wounds contaminated by nearby flora.
  • For these strict anaerobes multiply at a focus in animal tissue if the redox potential of the area is lowered.
  • This can occur through trauma and necrosis, ischaemia, parasitic invasion or concomitant multiplication of facultative anaerobes.
  • B. nodosus produces keratinolytic enzymes and F. necrophorum produces leukotoxin – which protects Corynebacterium pyogenes from phagocytosis. C. pyogenes produces a diffusible factor that stimulates the proliferation of Fusobacterium in tissue.
  • The conditions caused by these non-sporing anaerobes include soft tis­sue abscesses and cellulitis, post-operative wound infections, periodontal abscesses, aspiration pneumonia, lung and liver abscesses, peritonitis, pleuritis, myometritis, osteomyelitis, mastitis and foot rot. The excessive odour is due to production of volatile fatty acids.
  • Diseases caused by Bacteroides and Fusobacterium species
Species
Host(s)
Disease
Dichelobacter (Bacteroides) nodosus
Sheep
Cattle, Goats and Pigs
Contagious (virulent) foot rot
Contagious interdigital dermatitis
B. melaninogenicus
Cattle
Foot rot
B. asaccharolyticus
Dogs, cats, horses, cattle
Osteomyelitis
B. fragilis
Calves, lambs, foals, piglets
Diarrhoeal disease
Fusobacterium necrophorum
(associated with Corynebacterium pyognes )
Sheep
Cattle
Horses
Pigs
Chickens
Foot abscess , Ovine interdigital dermatitis (Scald)
Calf diphtheria
Thrush - infections of front of hoof.
Ulcerative stomatitis
("sore mouth" or "Bull nose" - via injury from fitting nose rings)
Necrotic enteritis
Avian diptheria (Secondary to fowl pox)

 
Last modified: Monday, 4 June 2012, 5:45 AM