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Created page with '===Overview=== *Mostly non-pathogenic environmental organisms *''Bacillus anthracis'' causes anthrax *Anthrax is a severe disease affecting all mammals worldwide *Ruminants …'
===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 outgrowths from 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 - WikiBlood|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, [[Haemostasis - Pathology#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 found 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
*''CAR bacillus'' in [[Respiratory Bacterial Infections - Pathology#CAR bacillus|URT infection in cattle]] and [[Respiratory Bacterial Infections - Pathology#In Rabbits|URT infection in rabbits]]
[[Category:Bacteria]][[Category:Gram_positive_bacteria]]
*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 outgrowths from 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 - WikiBlood|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, [[Haemostasis - Pathology#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 found 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
*''CAR bacillus'' in [[Respiratory Bacterial Infections - Pathology#CAR bacillus|URT infection in cattle]] and [[Respiratory Bacterial Infections - Pathology#In Rabbits|URT infection in rabbits]]
[[Category:Bacteria]][[Category:Gram_positive_bacteria]]