Difference between revisions of "Bacillus species"
Jump to navigation
Jump to search
| Line 11: | Line 11: | ||
*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 | ||
| Line 31: | Line 34: | ||
===''Bacillus anthracis''=== | ===''Bacillus anthracis''=== | ||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
* | * | ||
| + | *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: | ||
| + | ** | ||
Revision as of 12:50, 17 May 2008
- CAR bacillus in URT infection in cattle and URT infection in rabbits
- Can cause vascular fragility, leading to haemorrhagic disease.
Overview
- Mostly non-pathogenic environmental organisms
- 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 cereus causes food poisoning in humans and mastitis in cows
Characteristics
- Large, Gram positive rods
- Produce endospores
- Aerobes or facultative anaerobes
- Grow on non-enriched media
- Motile
- Catalase positive, oxidase negative
- Bacillus anthracis colonies are up to 5mm diameter, flat, dry, grey, with a ground-glass appearance; curled outgrowthsfrom the edge of the colony give a 'medusa head' appearance; non-haemolytic (differentiate from Bacillus cereus)
- Bacillus licheniformis forms dull, rough, wrinkled colonies, with hair-like outgrowths
- Biochemical tests for identification
- Can often tolerate adverse environmental conditions
Bacillus anthracis
- 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:
Bacillus licheniformis
- Widespread in the environment
- Associated with food spoilage
- Abortion in cattle and sheep, possibly from spoiled silage or hay