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Histotoxic clostridia
Bacteriology lectures
By
Dr. Zina Alshami
Diseases caused by Histotoxic clostridia occur
throw 2-typesof infection:
1- endogenous infection including:
• Blackleg
• infectious necrotic hepatitis
• bacillary haemoglobinuria
2- The exogenous infections including:
• malignant oedema
• gas gangrene
Blackleg
C. chauvoei,
Malignant oedema and gas gangrene
C. septicum causes malignant oedema
C. perfringens type A causes gas gangrene.
Caused by C. septicum
Infectious necrotic hepatitis (black disease)
caused by exotoxins of
C.novyi
type
B
replicating in liver tissue
which has been damaged
by immature Fasciola
hepatica
or
other
migrating parasites.
Bacillary haemoglobinuria
• endogenous infection caused by C. haemolyticum, endospores are dormant
in the liver, in Kupffer cells. Fluke migration facilitates spore germination
and clostridial replication The α toxin, a phospholipase produced by
vegetative cells, causes intravascular haemolysis in addition to hepatic
necrosis. Extensive red cell destruction lead to Haemoglobinuria.
Diagnosis
1. Fluorescent
antibody
techniques
(FAT).
2. C.
perfringens
is
cultured
anaerobically on blood agar at 37°C
for
48
hours.
Colonies
appear
surrounded by a zone of double
haemolysis.
Nagler reaction produced by Clostridium
perfringens growing on egg yolk agar.
The
Nagler
reaction,
a
plate
neutralization test, identifies the α
toxin of C. perfringens, which has
lecithinase activity.
CAMP test
• Positive CAMP test occurs with
Streptococcus
agalactiae
A
diffusible factor released by S.
agalactiae
enhances
the
partial
haemolysis produced by the α toxin
of C. perfringens.
•
PCR techniques
Treatment and control
• Penicillin or broad-spectrum antibiotics.
• Vaccination, usually with bacterin and toxoid components in adjuvant.