Histotoxic & Enteropathogenic Clostridia Flashcards
How do histotoxic Clostridia cause infection?
present as latent spores in muscle and liver where, once activated by anaerobic conditions, can secrete exotoxins that induce local tissue necrosis and lethal systemic effects
- each species produces different toxins
Where are histotoxic Clostridia endospores widely distributed?
in the environment and can persist for long period in the soil where it can be ingested and moved from the GI tract to liver and muscle
How is egg yolk agar used as a differential/enriched media for growing Clostridium species?
differentiates species based on lecithinase activity
- lecithovitellin is a normal lipoprotein in egg yolk and can be split by lecithinase into phosphorylocholine and insoluble diglyceride, which results in the formation of precipitate in the medium (white opaque zone)
What is most affected by C. chauvoei in black leg?
thick-muscled areas become necrotic, emphysematous, and edematous
What is the pathogenesis of endogenous and exogenous infections caused by histotoxic infections?
ENDOGENOUS: spores in intestinal lumen —> tissue (phagocytes) —> tissue injury (reduced oxygen) —> spore germination —> vegetative bacteria produce exotoxins —> necrosis and toxemia
EXOGENOUS: infected wounds
What 4 Clostridium species cause malignant edema? How is it commonly caused?
- C. perfringens type A
- C. noyvi
- C. chauvoei
- C. sordellii
puncture wound that becomes infectious (exogenous)
How does malignant edema present?
dark hemorrhagic muscle, edema in subcutaneous tissue, fibrin production
What causes Braxy? What is it?
C. septicum
infectious disease which causes sudden death in sheep, commonly occurs in winter, when sheep eat frosted root crops or frosted grass, which damages the mucosa of the abomasum, allowing it to enter, causing abomasitis and a fatal bacteremia
What causes black disease? What is it typically associated with? How does it present?
C. noyvi
spores awakened by parasitic infection caused by Fasciola hepatica
gas bubbles on liver causing a spongy appearance
What is the most distinguishing feature of sudden death in sows?
Black disease caused by C. noyvi
What causes bacillary hemoglobinuria? What are 2 common signs?
C. hemolyticum
- dark purple/red “port wine” colored urine and dark-colored feces
- yellow color or pale gum and eye sclera (jaundice) with pinpoint red blood spots (petechia)
- caused by hemoglobin breakdown
What determines resistance to histotoxic Clostridium resistance?
circulating antibodies to toxins and cellular components
In what 2 ways can a laboratory diagnosis of histotoxic Clostridium infection be reached?
- immunofluorescence of infected tissue smears show sporulated Gram-positive rods
- detection in tissue or identification in culture using PCR (flagellin and other genes)
What are 2 requirements to histotoxic Clostridium isolation?
- strict anaerobic conditions
- culture medium rich in cysteine and water-soluble vitamins
Treatment for histotoxic Clostridium infections is often distressing. What treatment is done?
IV penicillin
How are histotoxic Clostridium infections controlled in cattle, ewes, and lambs? What is recommended when cases are first observed?
CATTLE are vaccinated at 3-6 months (should precede exposure)
pregnant EWES are vaccinated 3 weeks prior to parturition
LAMBS are vaccinated by their first year
change of pasture
What Clostridium species is enteropathogenic? Where are they typically found?
C. perfringens type A, B, C, D, E
GI tract
What are 3 factors that predispose sheep to the development of C. perfringens?
- low proteolytic activity in the neonatal intestine (unable to break down toxins)
- incomplete establishment of normal intestinal flora in neonates
- dietary influences in older animals - abrupt change to or gorging on a rich diet; intestinal hypomotility
What is the common toxin produced by all enteropathogenic Clostridia?
α-toxin
- used for diagnostics in hemolytic activity (hot-cold lysis)
What is Type A enterotoxemia responsible for? What makes it able to do this?
tissue destruction caused by active toxins and connective tissue toxins