Monday, September 12, 2011

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Anthrax


It is caused by an organism known as Bacillus anthracis. The latter is a gram positive, spore-forming rod that is found in soil. The spores can remain viable for years.

Anthrax came to public notice in September 2001 when it was used as a bioweapon delivered through the U.S Postal System causing infection in 22 persons of whom 5 died. In the past i.e. during World War II , anthrax was studied mainly for its potential use as a biological weapon but following the Biological and Toxin Weapons Convention Treaty in 1972, such research was no longer allowed. Still, some nations and extremist groups do work on this agent secretly.

There are 3 major clinical forms of anthrax:
11)      Gastrointestinal anthrax – from ingestion of contaminated meat
22)      Cutaneous  anthrax – from introduction of spores through opening in skin
33)      Inhalational anthrax- inhalation of spores that deposit in the alveolar spaces.

The inhalational form is the one usually used for bioterrorist attack. Once deposited in the alveolar spaces, the macrophages phagocytose them. They are then transported to the mediastinal and peribronchial lymph nodes where they germinate to cause active bacterial growth. The bacteria produce edema toxins and lethal toxin which are later disseminated by blood.

Incubation period: 1-12 days but can go up to 60 days.

Clinical Features:
fever, malaise, chest and abdominal discomfort.

Diagnosis:
Culture and then microscopy with Gram’s stain. Wright’s stain of peripheral blood film. PCR.
CXR – evolvement from hilar prominence to progressive enlargement of the mediastinum and eventually pleural effusions.

Treatment:
Successful treatment is possible if the condition is diagnosed quickly and antibiotic treatment started promptly.
Ciprofloxacin 500 mg BD for 60 days.
Doxycycline 100mg BD for 60 days.  



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