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Swedish University of Agricultural Sciences

Veterinary bacteriology: information about important bacteria
Veterinary bacteriology


Species/Subspecies: Bacillus anthracis
Categories: Zoonotic; spore forming; notifiable diseases and bacteria
Etymology: Genus name: small rod
Species epithet: Greek anthrax coal, in reference to the black skin lesions of cutaneous anthrax
Significance:The consequences of an anthrax outbreak are serious. In Sweden only sporadic cases in animals have been reported between the years 1910 and 1971. There was an outbreak in pigs and cattle 1956-57. Thereafter three more outbreaks have been reported (1981 in Uppland, 2008 in Halland, and 2016 in Östergötland).
  [Very important]   
Taxonomy:
Phylum
Firmicutes
Class
Bacilli
Order
Bacillales
Family
Bacillaceae 
Genus
Bacillus
Type Strain: ATCC 14578 = NCTC 10340
Macromorphology (smell):
 
Grey-white large irregular colonies (diameter 3-5 mm) without hemolysis, colonies become mucoid in the presence of CO2 and NaHCO3
Micromorphology:
     
 
Large non motile rods (1.0-1.2 x 3-5 µm) in chains. The rods have characteristic edgy corners (sometimes not visible at capsule staining). Can produce oval spores located centrally in the bacterial cell (sporangium).
Gram +/Gram -:G+
Metabolism: Facultatively anaerobic
Catalase/Oxidase:+/-
Other Enzymes: Lecithinase+
Biochemical Tests: Voges-Proskauer+
Fermentation of carbohydrates:
D-glucoselactosemaltoseL-rhamnosesucrose
+-+-+
L-arabinosecellobioseD-mannitolsalicintrehalose
----+
glycerolinulinraffinoseD-sorbitolstarch
----+
Gas production: Glucose (gas) -.
Other carbohydrates: D-xylose -.
Spec. Char.: B. anthracis can be distinguished from B. cereus and B. turingienses through the capsule, tiamine (vitamin B) dependent growth and that it is lysed by gamma phages
Reservoir: Soil can contain B. anthracis spores
Disease:
HostsDiseaseClinical picture
Cattle, sheepAnthraxFatal and peracute or acute septicaemia, fever (up to 42°C). Post mortem rapid bloating, incomplete rigor mortis, haemorrhages, oedema and large soft spleen
PigsAnthraxSubacute with oedematous swelling in pharyngeal region
HorsesAnthraxSubacute with subcutanous oedema, swelling in pharyngeal region, septicaemia, colic and haemorrhagic enteritis
HumansAnthraxOccurs in three forms depending on route of infection: cutaneous, pulmonary and gastrointestinal. The cutanous form most common in humans and the pulmonary form in ruminants. Fatal in absence of early treatment.
Virulence Factors: Carries two plasmids (pX01 and pX02) with virulence genes. The plasmid pX01 contains toxin genes and pX02 genes for synthesis of the capsule, which consists of poly-D-glutamate. The toxin consists of three thermo labile protein components: factor I (edema factor), II (protective antigen) and III (lethal factor). The factors I and III block important signal systems in the cell. The capsule is composed of poly-D-glutamic acid and inhibits phagocytosis. B. anthracis also produces two siderophores (iron-binding substances), petrobactin och bacillibactin.
Genome Sequence:
Acc-noStrainSize (bp)Genome
NC_007530 Ames Ancestor 5 227 419 1c + 2c 

16S rRNA Seq.:
Acc-noStrainNumber of NTOperon
AB190217 (T) 1306 11 

Taxonomy/phylogeny:
 
There are about 250 species of the genus Bacillus. Bacillus anthracis is very closely related to Bacillus cereus and Bacillus thuringiensis, but the latter lack the plasmids pX01 and pX02.
Legislation: Anthrax is a notifiable disease. Bacillus anthracis belongs to category A as a potential bioterrorism agent according to NIAID.
Comment:Bacillus anthracis spores are very resistant and outbreaks can often be traced to old anthrax graves. If the grave is disturbed and the spores come up to the surface they can germinate (become vegetative cells).
Reference(s): No. 87, 100, 121
Updated:2021-03-16

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