Difference between revisions of "Bacillus anthracis"

Latest revision as of 01:28, 19 May 2016

Bacillus anthracis
Phylum	Firmicutes
Class	Bacilli
Order	Bacillales
Family	Bacillaceae
Genus	Bacillus
Species	B. anthracis

photomicrograph of Bacillus anthracis bacteria using Gram-stain technique. (CDC unknown, Wikimedia commons)

Overview

Bacillus anthracis is a species of Bacillus bacteria. B.anthracis is a saprophyte in soil. Its endospore formation allows persistence and spread as they survive decades in the soil. Infection usually occurs by ingestion of spores and penetration through damaged mucosa. Outbreaks occur in herbivore's grazing pastures contaminated by spores from buried carcases.

Pathogenesis

Bacillus anthracis causes anthrax.

Spores of the bacteria germinate at the site of entry and spread via lymphatics to the bloodstream, where they multiply and produce toxin. The extracellular toxin (holotoxin) is 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 and protective antigen binds to the cell receptor to allow action of the other factors. The toxin kills phagocytes, increases capillary permeability and interferes with the clotting cascade.

They have a capsule composed of a homopolymer of D-isomer of glutamic acid. It allows survival in the body by resisting phagocytosis. The capsule and toxin (encoded by separate plasmids) are required for virulence. The capsule stains mauve with polychrome methylene blue in the MacFadyean's reaction. This can be used to identify anthrax in blood samples. Bacilli appear as chains of dark blue, square-ended rods surounded with the capsule.

Bacillus anthracis causes tissues to darken and swell due to oedema and necrosis. It causes capillary thrombosis, the leakage of fluid through damaged capillary endothelium. Systemic shock from circulatory collapse, haemorrhagic disease and oedema lead to death of the animal. It causes severe systemic disease that can result in enteritis and peritonitis in pigs.

Bacillus anthracis Learning Resources
Vetstream To reach the Vetstream content, please select	Canis, Felis, Lapis or Equis
Literature Search Search for recent publications via CAB Abstract (CABI log in required)	Bacillus anthracis publications since 2000

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-[[Image:human anthrax.jpg|right|thumb|125px|<small><center>'''Anthrax (human)'''. Courtesy of T. Scase</center></small>]]
+{{OpenPagesTop}}
+{{Taxobox
+|name               =''Bacillus anthracis''
+|phylum             =Firmicutes
+|class              =Bacilli
+|order              =Bacillales
+|family             =Bacillaceae
+|genus              =Bacillus
+|species            =''B. anthracis''
+}}
-*Epidemiology:
+[[File:Bacillus anthracis Gram.jpg|right|thumb|250px|<small><center> photomicrograph of ''Bacillus anthracis'' bacteria using Gram-stain technique. (CDC unknown, Wikimedia commons)</center></small>]]
-**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 [[Septicaemia and Enteritis, Bacterial|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
+==Overview==
+''Bacillus anthracis'' is a species of ''[[:Category:Bacillus species|Bacillus]]'' bacteria. ''B.anthracis'' is a saprophyte in soil. Its endospore formation allows persistence and spread as they survive decades in the soil. Infection usually occurs by ingestion of spores and penetration through damaged mucosa. Outbreaks occur in herbivore's grazing pastures contaminated by spores from buried carcases.
+==Pathogenesis==
-* Causes severe systemic disease that can result in [[Septicaemia and Enteritis, Bacterial|enteritis]].
+''Bacillus anthracis'' causes [[Anthrax|anthrax]].
-*[[Peritoneal Cavity Inflammatory - Pathology#In pigs|Peritonitis in pigs]]
-[[Category:Bacillus_species]][[Category:Cattle]][[Category:Sheep]][[Category:Pig]][[Category:Horse]][[Category:Dog]]
+Spores of the bacteria germinate at the site of entry and spread via lymphatics to the bloodstream, where they multiply and produce toxin. The extracellular toxin (holotoxin) is 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|neutrophils]]. Lethal factor causes release of cytokines from macrophages and protective antigen binds to the cell receptor to allow action of the other factors. The toxin kills phagocytes, increases capillary permeability and interferes with  the clotting cascade.
+They have a capsule composed of a homopolymer of D-isomer of glutamic acid. It allows survival in the body by resisting phagocytosis. The capsule and toxin (encoded by separate plasmids) are required for virulence.
+The capsule stains mauve with polychrome methylene blue in the MacFadyean's reaction. This can be used to identify anthrax in blood samples. Bacilli appear as chains of dark blue, square-ended rods surounded with the capsule.
+''Bacillus anthracis'' causes tissues to darken and swell due to oedema and necrosis. It causes capillary thrombosis, the leakage of fluid through damaged capillary endothelium. Systemic shock from circulatory collapse, haemorrhagic disease and oedema lead to death of the animal. It causes severe systemic disease that can result in [[:Category:Intestine - Inflammatory Pathology by Cause|enteritis]] and [[Peritonitis #In pigs|peritonitis in pigs]].
+{{Learning
+|literature search = [http://www.cabdirect.org/search.html?rowId=1&options1=AND&q1=%22Bacillus+anthracis%22&occuring1=title&rowId=2&options2=AND&q2=&occuring2=freetext&rowId=3&options3=AND&q3=&occuring3=freetext&publishedstart=2000&publishedend=yyyy&calendarInput=yyyy-mm-dd&la=any&it=any&show=all&x=47&y=11 ''Bacillus anthracis'' publications since 2000]
+|Vetstream = [https://www.vetstream.com/canis/Content/Bug/bug00348.asp Bacillus anthracis]}}
+{{review}}
+{{OpenPages}}
+[[Category:Bacillus_species]]
+[[Category:Expert_Review]]

Difference between revisions of "Bacillus anthracis"

Latest revision as of 01:28, 19 May 2016

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