Toxins

TOXINS

Classification

  • C.welchii is one of the most prolific of toxin producing bacteria forming at least 12 different toxins , besides many other enzymes and biological active substances.
C. perfringens
Major toxins
Type
Alpha
Beta
Epsilon
Iota
A
+
-
-
-
B
+
+
+
-
C
+
+
-
-
D
+
-
+
-
E
+
-
-
+
  • Alpha toxin is produced by all types. Mostly by type A strains. It is lethal, dermonecrotic and haemolytic.
  • This is a lecithinase C (phospholipase) that attacks cell membranes causing cell death and destruction and also responsible for Nagler’s reaction .
  • It is haemolytic for the red cells of most species except horse and goat. This toxin gives a zone of partial haemolysis on blood agar.
  • The haemolysis is of hot-cold variety being best seen after incubation at 370C followed by chilling at 40C.
  • Beta toxin is lethal and necrotising. It is sensitive to trypsin and this explains the predilection of types B and C for neonates as colostrum has anti trypsin activity.
  • It is a labile toxin and may be destroyed if there is a delay in small intestinal contents, containing the toxin, reaching the laboratory.
  • Epsilon toxin is secreted as a protoxin (proto toxin) and is activated in the intestines by proteases such as trypsin.
  • Pulpy kidney disease is not usually seen in neonatal lambs as colostrum contains an antitrypsin factor that can prevent the epsilon toxin being activated.
  • The toxin itself increases gut permeability, assuring absorption of the toxin into the blood stream.
  • It damages vascular endothelium (including blood vessels in the brain) leading to fluid loss and edema.
  • This epsilon toxin can be regarded as an enterotoxin and neurotoxin.
  • Iota toxin is also produced as a protoxin and is not unique to C.perfringens type E as it is also formed by C.spiroforme and C.difficile
  • Besides several minor toxins are produced such as the theta (haemolysin), Kappa (collagenase), lambda (Proteinase), Mu(hyaluronidase) and Nu(DNase) – all these may contribute to tissue damage.
  • Based on the type of toxin productions, Clostridium perfringens are classified into 5 types

C.perfringens types
Major toxins
Host
Disease
A
Enterotoxins
Human
Food poisoning
Alpha
Lambs
Broiler chickens
Enterotoxaemic jaundice
Necrotic enteritis
B
Beta and alpha
Lambs under 3 weeks old
Lamb dysentry
C
Beta and alpha
Piglets 1-3days old
Haemorrhagic enteritis
(Clostridial enteritis)
Broiler chickens
(2 weeks old)
Necrotic enteritis
Adult sheep and goats
Struck
D
Epsilon
Sheep all ages (except neonates)
Pulpy kidney disease (over eating disease)
E
Iota and alpha
Calves and lambs
Enterotoxaemia (Haemorrhagic enteritis)

 
Last modified: Monday, 4 June 2012, 4:30 AM