Bacillus anthracis

Bacillus anthracis
Photomicrograph of Bacillus anthracis (fuchsin-methylene blue spore stain).
Scientific classification
Kingdom:	Bacteria
Phylum:	Firmicutes
Class:	Bacilli
Order:	Bacillales
Family:	Bacillaceae
Genus:	Bacillus
Species:	B. anthracis
Binomial name
Bacillus anthracis Cohn 1872

Structure of Bacillus anthracis.

Bacillus anthracis is a Gram-positive spore-forming, rod-shaped bacterium, with a width of 1-1.2µm and a length of 3-5µm. It can be grown in an ordinary nutrient medium under aerobic or anaerobic conditions. It is the only bacterium with a protein capsule (D-glutamate), and the only pathogenic bacteria to carry its own adenylyl cyclase virulence factor (edema factor). It bears close genotypical and phenotypical resemblance to Bacillus cereus and Bacillus thuringiensis. All three species share cellular dimensions and morphology. All form oval spores located centrally in a non-swollen sporangium. Bacillus anthracis spores in particular are highly resilient, surviving extremes of temperature, low-nutrient environments, and harsh chemical treatment over decades or centuries.

Historical background

Casimir Davaine first isolated this bacterium from the blood of sheep suffering from anthrax.^[1] B. anthracis was the first bacterium conclusively demonstrated to cause disease, by Robert Koch in 1877.^[2] The species name anthracis is from the Greek anthrakis (ἄνθραξ), meaning coal and referring to the most common form of the disease, cutaneous anthrax, in which large black skin lesions are formed.

Pathogenesis

Three forms of anthrax disease are recognized based on their form of inoculation.

Cutaneous

the most common form (95%), causes a localized inflammatory black necrotic lesion (eschar)

Pulmonary

highly fatal and characterized by sudden massive chest edema followed by cardiovascular shock

Gastrointestinal

rare but also fatal (causes death to 25%) type results from ingestion of spores

Treatment

Infections with B. anthracis can be treated with β-lactam antibiotics such as penicillin, and others which are active against Gram-positive bacteria.^[3]

Laboratory research

Components of tea, such as polyphenols, have the ability to inhibit the activity both of bacillus anthracis and its toxin considerably; spores, however, are not affected. The addition of milk to the tea completely inhibits its antibacterial activity against anthrax^[4]. Activity against the anthrax bacillum in the laboratory does not prove that drinking tea affects the course of an infection, since it is unknown how these polyphenols are absorbed and distributed within the body.

External links

• Hazards in Animal Research Database - Bacillus anthracis
• Pathema-Bacillus Resource

References