Difference between revisions of "Bacillus species"
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===''Bacillus anthracis''=== | ===''Bacillus anthracis''=== | ||
− | * | + | *Epidemiology: |
+ | **Endospore formation allows persistence and spread | ||
+ | **Endospores survive decades in the soil | ||
+ | **Outbreaks in herbivores grazing pastures contaminated by spores from buried carcases | ||
+ | **Infection usually by ingestion of spores | ||
*Pathogenesis and pathogenicity: | *Pathogenesis and pathogenicity: | ||
**Saprophyte in soil | **Saprophyte in soil | ||
Line 47: | Line 51: | ||
**Protective factor binds to the cell receptor to allow action of the other factors | **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 | **The toxin kills phagocytes, increases capillary permeability and interferes with clooting cascade | ||
− | |||
− | |||
*Clinical signs: | *Clinical signs: | ||
− | ** | + | **Cattle: |
+ | ***Fatal peracute septicaemia | ||
+ | ***Capillary thrombosis; leakage of fluid through damaged capillary endothelium | ||
+ | ***Systemic shock from circulatory collapse, haemorrhage and oedema lead to death of the animal | ||
+ | **Pigs: | ||
+ | ***Subacute anthrax with oedematous pharyngeal swelling; intestinal form with high mortality | ||
+ | **Horses: | ||
+ | ***Subacute anthrax with localised oedema; septicaemia with colic and enteritis | ||
Line 58: | Line 67: | ||
*Associated with food spoilage | *Associated with food spoilage | ||
*Abortion in cattle and sheep, possibly from spoiled silage or hay | *Abortion in cattle and sheep, possibly from spoiled silage or hay | ||
+ | |||
+ | |||
+ | ===''Bacillus cereus''=== | ||
+ | |||
+ | *Mastitis in cattle | ||
+ | *Food poisoning and eye infections in humans |
Revision as of 13:01, 17 May 2008
- CAR bacillus in URT infection in cattle and URT infection in rabbits
- Can cause vascular fragility, leading to haemorrhagic disease.
- Causes severe systemic disease that can result in enteritis.
- peritonitis in pigs
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
- Epidemiology:
- Endospore formation allows persistence and spread
- Endospores survive decades in the soil
- Outbreaks in herbivores grazing pastures contaminated by spores from buried carcases
- Infection usually by ingestion of spores
- 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
- Clinical signs:
- Cattle:
- Fatal peracute septicaemia
- Capillary thrombosis; leakage of fluid through damaged capillary endothelium
- Systemic shock from circulatory collapse, haemorrhage and oedema lead to death of the animal
- Pigs:
- Subacute anthrax with oedematous pharyngeal swelling; intestinal form with high mortality
- Horses:
- Subacute anthrax with localised oedema; septicaemia with colic and enteritis
- Cattle:
Bacillus licheniformis
- Widespread in the environment
- Associated with food spoilage
- Abortion in cattle and sheep, possibly from spoiled silage or hay
Bacillus cereus
- Mastitis in cattle
- Food poisoning and eye infections in humans