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*Mostly non-pathogenic environmental organisms
*Mostly non-pathogenic environmental organisms
*''Bacillus anthracis'' causes anthrax
*''Bacillus anthracis'' causes anthrax
*Anthrax is a severe disease affecting all mammals worldwide
*Ruminants are highly susceptible to anthrax, dying of a septicaemic form
*Pigs and horses are moderately susceptible, but carnivores are fairly resistant
*''Bacillus licheniformis'' may cause shoradic abortions in cattle and sheep
*''Bacillus licheniformis'' may cause shoradic abortions in cattle and sheep
*''Bacillus cereus'' causes food poisoning in humans and mastitis in cows
*''Bacillus cereus'' causes food poisoning in humans and mastitis in cows
===''Bacillus anthracis''===
===''Bacillus anthracis''===
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*Pathogenesis and pathogenicity:
**Saprophyte in soil
**Capsule composed of homopolymer of D-isomer of glutamic acid allows survival in the body by resisting phagocytosis
**Capsule stains mauve with polychrome methylene blue in the MacFadyean's reaction - identify anthrax in blood samples
**Bacilli appear as chains of dark blue, square-ended rods surounded with the capsule
**Extracellular toxin (holotoxin) composed of oedema factor, protective factor and lethal factor
**Oedema factor is an adenylate cyclase which increases intracellular cAMP concetrations, damaging phagocytes
**Protective factor binds to the cell receptor to allow action of the other factors
**The toxin kills phagocytes, increases capillary permeability and interferes with clooting cascade
**Capillary thrombosis; leakage of fluid through damaged capillary endothelium
**Systemic shock from circulatory collapse, haemorrhage and oedema lead to death of the animal
*Clinical signs:
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