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| − | <big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>
| + | #REDIRECT[[:Category:Bacillus species]] |
| − | <big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big>
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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
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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
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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, [[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
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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#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 foung 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 [[Bacterial infections#CAR bacillus|URT infection in cattle]] and [[Bacterial infections#In Rabbits|URT infection in rabbits]]
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