All about the etiologic agent of Anthrax.

https://www.cdc.gov/anthrax/news-multimedia/animations-and-videos.html

The origin of Anthrax is believed to be Egypt and Mesopotamia. It was present during the times of Moses as the fifth Egyptian plagues that affected oven, human, camel etc. (CDC,2017)

The causative agent for Anthrax isBacillus anthracis. Its name was derived from the Greek word for coal, describing the black dry scab observed on affected organisms. B. anthracis is a nonmotile, rod-shaped gram- positive obligate bacteria is an aerobic that ranges from 1–1.5 × 3–10 μm in size. The bacteria exist as oval dormant spore naturally existing in the soil until, introduced via inhalation by their host. They are activated into their vegetative forms triggered by the availability of resources.(Fig 1)

Fig 1.Two forms of B. anthracis in the spore and vegetative form. https://www.cdc.gov/anthrax/basics/index.html

B. anthracis has virulence plasmids pXO1 that has a three toxins lethal factor, edema factor and protective antigen and pXO2 is involved in the production of polyglutamyl capsule. Hence pXO1 is responsible for necrosis ,edema and  bleeding  and PXO2 capsule production prevents phagocytes from engulfing the B. anthracis in its vegetative form in the host.(Leppla ,1982).The toxin produced is an A-B toxin ,where the protective antigen toxin is the medium that delivers the edema and lethal toxin from the outside to inside  of the host cell.(Lacy & Collier, 2002)

The dehydrated spore is surrounded by a membrane and a specialized cortex that limits the exchange of water and solute to and from the spore. This is the protective outer layer that withstands chemical, enzymatic and desiccation. (Setlow, 2006).

B. anthracis cultured at 37°C in sheep blood agar has an off-white appearance, non-hemolytic, comma shaped slightly cover with irregular edges. (Fig 2) It is observed purple rod unicellular or chain or rods when stained with gram stain and observed under the microscope. (Fig 1)

Photo of Bacillus anthracis colonies in blood agar. Courtesy of CDC/Larry Stauffer.

Fig 3. Mucoid colonies of Bacillus anthracis due to production of polyglutamyl capsule. http://textbookofbacteriology.net/Anthrax_2.html

This is all for now about the infamous Anthrax bacteria..

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REFERENCE

1.CDC ( 2017): Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)

2. Leppla SH.(1982)Anthrax toxin edema factor; a bacterial adenylate cyclase that increases cyclic AMP concentrations of eukaryotic cells. Proc Natl Acad Sci U S A1982;79:3162–6. [PMC free article][PubMed] [Google Scholar]

3.Lacy D.B. & Collier R.J. (2002) Structure and Function of Anthrax Toxin. In: Koehler T.M.  Anthrax. Current Topics in Microbiology and Immunology, vol 271. Springer, Berlin, Heidelberg. https://link.springer.com/chapter/10.1007%2F978-3-662-05767-4_4#citeas

4.Setlow P.(2006) Spores of Bacillus subtilis: their resistance to and killing by radiation, heat and chemicals. J Appl Microbiol101, 514–525.

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