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#REDIRECT[[:Category:Bacillus species]]
 
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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 outgrowths from 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
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**Endospores survive decades in the soil
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**Outbreaks in herbivores grazing pastures contaminated by spores from buried carcases
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**Infection usually by ingestion of spores and penetration through damaged mucosa
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*Pathogenesis and pathogenicity:
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**Spores germinate at site of entry and spread via lymphatics to bloodstream, where they multiply and produce toxin
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**Capsule and toxin (encoded by separate plasmids) required for virulence
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**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 - WikiBlood|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
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**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, [[Haemostasis - Pathology#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 - Pathology#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
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**Pigs:
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***Subacute anthrax with oedematous swelling of throat, head and regional lymph nodes
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***Intestinal form with high mortality - dysentry due to haemorrhagic enteric lesions
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***[[Peritoneal Cavity Inflammatory - Pathology#In pigs|Peritonitis]]
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**Horses:
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***Subacute anthrax with subcutaneous oedema of thorax, abdomen and legs following entrance of spores into abrasions
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***Septicaemia with colic and dysentry due to haemorrhagic enteritis from ingestion of spores; ecchymoses and splenomegaly
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**Dogs
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***Rarely affected, but similar disease to that found in pigs
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**Humans
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***Cutaneous anthrax - localised lesion from entrance into abrasion which can cause septicaemia
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***Pulmonary anthrax - inhalation of spores
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***Intestinal anthrax - ingestion of infective material
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*Diagnosis:
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**Post mortem: bloat, incomplete rigor mortis, ecchymoses, oedema, dark unclotted blood from orifices, blooy fluid in body cavities, splenomegaly
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**Blood smear from an ear or tail vein of ruminants, or peritoneal fluid from pigs stained with polychrome methylene blue
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**Chains of square-ended blue rods surrounded by mauve capsules
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**Culture on blood and MacConkey agar (no growth on MacConkey)
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**Biochemical tests
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*Treatment:
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**High doses of penicillin G or oxytetracylcine
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*Control:
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**Report suspected cases - notifiable
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**Spores destroyed by sterilisation
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**Endemic regions:
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***Live Sterne spore vaccine which produces toxin but has no capsule, therefore is non-pathogenic; stimulates protective antibody
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***Chemoprophylaxis with long-acting penicillin
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**Non-endemic regions after an outbreak:
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***Movement restrictions
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***Footbath with sporicidal disinfectant
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***Fumigate buildings with formaldehyde
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***Dispose carcases and contaminated material
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***Isolate in-contact animals
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===''Bacillus licheniformis''===
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*Widespread in the environment
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*Associated with food spoilage
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*Abortion in cattle and sheep, possibly from spoiled silage or hay
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===''Bacillus cereus''===
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*Mastitis in cattle
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*Food poisoning and eye infections in humans
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*''CAR bacillus'' in [[Respiratory Bacterial Infections - Pathology#CAR bacillus|URT infection in cattle]] and [[Respiratory Bacterial Infections - Pathology#In Rabbits|URT infection in rabbits]]
 
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