Difference between revisions of "Bacillus species"
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| Line 29: | Line 29: | ||
*Motile | *Motile | ||
*Catalase positive, oxidase negative | *Catalase positive, oxidase negative | ||
| − | *''Bacillus anthracis'' colonies are up to 5mm diameter, flat, dry, grey, with a ground-glass appearance; curled | + | *''Bacillus anthracis'' colonies are up to 5mm diameter, flat, dry, grey, with a ground-glass appearance; curled outgrowth sfrom 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 | *''Bacillus licheniformis'' forms dull, rough, wrinkled colonies, with hair-like outgrowths | ||
*Biochemical tests for identification | *Biochemical tests for identification | ||
| Line 53: | Line 53: | ||
**Protective antigen binds to the cell receptor to allow action of the other factors | **Protective antigen binds to the cell receptor to allow action of the other factors | ||
**The toxin kills phagocytes, increases capillary permeability and interferes with clotting cascade | **The toxin kills phagocytes, increases capillary permeability and interferes with clotting cascade | ||
| + | **Capillary thrombosis; leakage of fluid through damaged capillary endothelium | ||
| + | **Systemic shock from circulatory collapse, haemorrhage and oedema lead to death of the animal | ||
**Causes tissues to darken and swell due to oedema and necrosis | **Causes tissues to darken and swell due to oedema and necrosis | ||
*Clinical signs: | *Clinical signs: | ||
| − | **Cattle: | + | **Cattle/sheep: |
***Fatal peracute septicaemia | ***Fatal peracute septicaemia | ||
| − | *** | + | ***Animals usually found dead |
| − | *** | + | ***Pyrexia, depression, congested mucous membranes and petechiae before death |
| + | ***Abortion, subcutaneous oedema and dysentry in animals surviving more that one day | ||
| + | ***Post mortem: bloat, incomplete rigor mortis, ecchymoses, oedema, dark unclotted blood, blooy fluid in body cavities, splenomegaly | ||
**Pigs: | **Pigs: | ||
***Subacute anthrax with oedematous pharyngeal swelling; intestinal form with high mortality | ***Subacute anthrax with oedematous pharyngeal swelling; intestinal form with high mortality | ||
| + | |||
**Horses: | **Horses: | ||
***Subacute anthrax with localised oedema; septicaemia with colic and enteritis | ***Subacute anthrax with localised oedema; septicaemia with colic and enteritis | ||
Revision as of 13:15, 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 outgrowth sfrom 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:
- Saprophyte in soil
- 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:
- Capsule and toxin (encoded by separate plasmids) required for virulence
- 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 antigen and lethal factor
- Oedema factor is an adenylate cyclase which increases intracellular cAMP concetrations, causing fluid accumulation and damaging neutrophils
- Lethal factor causes release of cytokines from macrophages
- Protective antigen binds to the cell receptor to allow action of the other factors
- The toxin kills phagocytes, increases capillary permeability and interferes with clotting cascade
- Capillary thrombosis; leakage of fluid through damaged capillary endothelium
- Systemic shock from circulatory collapse, haemorrhage and oedema lead to death of the animal
- Causes tissues to darken and swell due to oedema and necrosis
- Clinical signs:
- Cattle/sheep:
- Fatal peracute septicaemia
- Animals usually found dead
- Pyrexia, depression, congested mucous membranes and petechiae before death
- Abortion, subcutaneous oedema and dysentry in animals surviving more that one day
- Post mortem: bloat, incomplete rigor mortis, ecchymoses, oedema, dark unclotted blood, blooy fluid in body cavities, splenomegaly
- Pigs:
- Subacute anthrax with oedematous pharyngeal swelling; intestinal form with high mortality
- Cattle/sheep:
- Horses:
- Subacute anthrax with localised oedema; septicaemia with colic and enteritis
- Horses:
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