Difference between revisions of "Bacillus species"

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#REDIRECT[[:Category:Bacillus species]]
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===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 and penetration through damaged mucosa
 +
*Pathogenesis and pathogenicity:
 +
**Spores germinate at site of entry and spread via lymphatics to bloodstream, where they multiply and produce toxin
 +
**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, [[General Pathology - Haemostasis#Haemorrhagic Disease Due To Vascular Fragility|haemorrhagic disease]] and oedema lead to death of the animal
 +
**Severe systemic disease that can result in [[Intestines Fibrinous/Haemorrhagic Enteritis - Pathology#Bacterial septicaemia and enteritis|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
 +
**Pigs:
 +
***Subacute anthrax with oedematous swelling of throat, head and regional lymph nodes
 +
***Intestinal form with high mortality - dysentry due to haemorrhagic enteric lesions
 +
***[[Peritoneal Cavity Inflammatory - Pathology#In pigs|Peritonitis]]
 +
**Horses:
 +
***Subacute anthrax with subcutaneous oedema of thorax, abdomen and legs following entrance of spores into abrasions
 +
***Septicaemia with colic and dysentry due to haemorrhagic enteritis from ingestion of spores; ecchymoses and splenomegaly
 +
**Dogs
 +
***Rarely affected, but similar disease to that foung in pigs
 +
**Humans
 +
***Cutaneous anthrax - localised lesion from entrance into abrasion which can cause septicaemia
 +
***Pulmonary anthrax - inhalation of spores
 +
***Intestinal anthrax - ingestion of infective material
 +
*Diagnosis:
 +
**Post mortem: bloat, incomplete rigor mortis, ecchymoses, oedema, dark unclotted blood from orifices, blooy fluid in body cavities, splenomegaly
 +
**Blood smear from an ear or tail vein of ruminants, or peritoneal fluid from pigs stained with polychrome methylene blue
 +
**Chains of square-ended blue rods surrounded by mauve capsules
 +
**Culture on blood and MacConkey agar (no growth on MacConkey)
 +
**Biochemical tests
 +
*Treatment:
 +
**High doses of penicillin G or oxytetracylcine
 +
*Control:
 +
**Report suspected cases - notifiable
 +
**Spores destroyed by sterilisation
 +
**Endemic regions:
 +
***Live Sterne spore vaccine which produces toxin but has no capsule, therefore is non-pathogenic; stimulates protective antibody
 +
***Chemoprophylaxis with long-acting penicillin
 +
**Non-endemic regions after an outbreak:
 +
***Movement restrictions
 +
***Footbath with sporicidal disinfectant
 +
***Fumigate buildings with formaldehyde
 +
***Dispose carcases and contaminated material
 +
***Isolate in-contact animals
 +
 
 +
 
 +
===''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
 +
 
 +
 
 +
*''CAR bacillus'' in [[Respiratory Bacterial Infections - Pathology#CAR bacillus|URT infection in cattle]] and [[Respiratory Bacterial Infections - Pathology#In Rabbits|URT infection in rabbits]]

Revision as of 09:39, 25 September 2008

 This article has been peer reviewed but is awaiting expert review. If you would like to help with this, please see more information about expert reviewing.


Infectious agents and parasitesWikiBugs Banner.png
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 and penetration through damaged mucosa
  • Pathogenesis and pathogenicity:
    • Spores germinate at site of entry and spread via lymphatics to bloodstream, where they multiply and produce toxin
    • 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
    • Pigs:
      • Subacute anthrax with oedematous swelling of throat, head and regional lymph nodes
      • Intestinal form with high mortality - dysentry due to haemorrhagic enteric lesions
      • Peritonitis
    • Horses:
      • Subacute anthrax with subcutaneous oedema of thorax, abdomen and legs following entrance of spores into abrasions
      • Septicaemia with colic and dysentry due to haemorrhagic enteritis from ingestion of spores; ecchymoses and splenomegaly
    • Dogs
      • Rarely affected, but similar disease to that foung in pigs
    • Humans
      • Cutaneous anthrax - localised lesion from entrance into abrasion which can cause septicaemia
      • Pulmonary anthrax - inhalation of spores
      • Intestinal anthrax - ingestion of infective material
  • Diagnosis:
    • Post mortem: bloat, incomplete rigor mortis, ecchymoses, oedema, dark unclotted blood from orifices, blooy fluid in body cavities, splenomegaly
    • Blood smear from an ear or tail vein of ruminants, or peritoneal fluid from pigs stained with polychrome methylene blue
    • Chains of square-ended blue rods surrounded by mauve capsules
    • Culture on blood and MacConkey agar (no growth on MacConkey)
    • Biochemical tests
  • Treatment:
    • High doses of penicillin G or oxytetracylcine
  • Control:
    • Report suspected cases - notifiable
    • Spores destroyed by sterilisation
    • Endemic regions:
      • Live Sterne spore vaccine which produces toxin but has no capsule, therefore is non-pathogenic; stimulates protective antibody
      • Chemoprophylaxis with long-acting penicillin
    • Non-endemic regions after an outbreak:
      • Movement restrictions
      • Footbath with sporicidal disinfectant
      • Fumigate buildings with formaldehyde
      • Dispose carcases and contaminated material
      • Isolate in-contact animals


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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