Anthrax

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Bacillus antracis [1]

Etiology/Bacteriology

Taxonomy

Domain: Bacteria
Phylum: Firmicutes
Class: Bacilli
Order: Bacillales
Family: Bacillaceae
Genus: Bacillus
Species: anthracis

Description

Bacillus anthracis is a Gram-positive facultative aerobic spore-forming bacterium found in the soil. B. anthracis derived its name from the Greek word for coal because this pathogen can cause black lesions on the victim's skin. The bacterium is non-motile and non-hemolytic on blood agar. B. anthracis is found mostly in spore-form in the environment, but when it has infected a host it will germinate and replicate in essentially all body tissues. When anthracis is in the spore form, it is resistant to most adverse environments and can survive for many decades.

Pathogenesis

Transmission

The most common way a human can contract anthrax is being in contact with an infected animal. Herbivore grazing animals can commonly contract anthrax because anthracis lives in the soil. A person may get anthrax by inhaling the spores from animal products, such as wool, have an open abrasion on the skin be exposed to the spores, or eating undercooked meat from an animal that was infected. More than 90% of anthrax cases are the cutaneous exposures.

Infectious dose, incubation, and colonization

The infectious dose of B. anthracis is not entirely clear. Some suggest 100 spores will cause infection while some analysis have shown as few as 1-3 spores will cause infection.

Clinical features

Cutaneous

Anthrax sore [2]

Inhalation

Inhalation of anthrax [3]

References

1. Conway, Tyrrell. “Genus conway”. “Microbe Wiki” 2013. Volume 1. p. 1-2.
2. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1769905/
3. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2784286/