Difference between revisions of "Bacillus species"

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#REDIRECT[[:Category:Bacillus species]]
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<big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>
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<big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big>
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*''CAR bacillus'' in [[Bacterial infections#CAR bacillus|URT infection in cattle]] and [[Bacterial infections#In Rabbits|URT infection in rabbits]]
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===Overview===
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*Mostly non-pathogenic environmental organisms
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*''Bacillus anthracis'' causes anthrax
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*Anthrax is a severe disease affecting all mammals worldwide
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*Ruminants are highly susceptible to anthrax, dying of a septicaemic form
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*Pigs and horses are moderately susceptible, but carnivores are fairly resistant
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*''Bacillus licheniformis'' may cause shoradic abortions in cattle and sheep
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*''Bacillus cereus'' causes food poisoning in humans and mastitis in cows
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===Characteristics===
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*Large, Gram positive rods
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*Produce endospores
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*Aerobes or facultative anaerobes
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*Grow on non-enriched media
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*Motile
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*Catalase positive, oxidase negative
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*''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'')
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*''Bacillus licheniformis'' forms dull, rough, wrinkled colonies, with hair-like outgrowths
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*Biochemical tests for identification
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*Can often tolerate adverse environmental conditions
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===''Bacillus anthracis''===
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*Epidemiology:
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**Saprophyte in soil
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**Endospore formation allows persistence and spread
 +
**Endospores survive decades in the soil
 +
**Outbreaks in herbivores grazing pastures contaminated by spores from buried carcases
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**Infection usually by ingestion of spores
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*Pathogenesis and pathogenicity:
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**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
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**Capsule stains mauve with polychrome methylene blue in the MacFadyean's reaction - identify anthrax in blood samples
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**Bacilli appear as chains of dark blue, square-ended rods surounded with the capsule
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**Extracellular toxin (holotoxin) composed of oedema factor, protective antigen and lethal factor
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**Oedema factor is an adenylate cyclase which increases intracellular cAMP concetrations, causing fluid accumulation and damaging neutrophils
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**Lethal factor causes release of cytokines from macrophages
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**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
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**Capillary thrombosis; leakage of fluid through damaged capillary endothelium
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**Systemic shock from circulatory collapse, [[General Pathology - Haemostasis#Haemorrhagic Disease Due To Vascular Fragility|haemorrhagic disease]] and oedema lead to death of the animal
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**Severe systemic disease that can result in [[Intestines - Fibrinous/ Haemorrhagic Enteritis#Bacterial septicaemia and enteritis|enteritis]]
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**Causes tissues to darken and swell due to oedema and necrosis
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*Clinical signs:
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**Cattle/sheep:
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***Fatal peracute septicaemia
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***Animals usually found dead
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***Pyrexia, depression, congested mucous membranes and petechiae before death
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***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
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**Pigs:
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***Subacute anthrax with oedematous pharyngeal swelling; intestinal form with high mortality
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****[[Peritoneal cavity - inflammatory#In pigs|Peritonitis in pigs]]
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**Horses:
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***Subacute anthrax with localised oedema; septicaemia with colic and enteritis
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===''Bacillus licheniformis''===
 +
 
 +
*Widespread in the environment
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*Associated with food spoilage
 +
*Abortion in cattle and sheep, possibly from spoiled silage or hay
 +
 
 +
 
 +
===''Bacillus cereus''===
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*Mastitis in cattle
 +
*Food poisoning and eye infections in humans

Revision as of 13:17, 17 May 2008

BACK TO INFECTIOUS AGENTS AND PARASITES
BACK TO BACTERIA



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, haemorrhagic disease and oedema lead to death of the animal
    • Severe systemic disease that can result in enteritis
    • 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
    • Horses:
      • Subacute anthrax with localised oedema; septicaemia with colic and enteritis


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
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