Diagnosis of Anthrax

Anthrax• Primarily a disease of domesticated & wild animals

– Herbivores such as sheep, cows, horses, goat• Natural reservoir is soil

– Does not depend on an animal reservoir making it hard to eradicate – Cannot be regularly cultivated from soils where there is an absence of endemic anthrax

• Anthrax is a disease of cattle, goats, and sheep caused by a bacterium, Bacillus anthracis• It is rare for humans to be infected

• Most infections that do occur are localized to small cuts in the skin whose edges turn black (hence the name “anthracis”, after anthracite coal).• The disease is deadly for humans because B. anthracis

produces lethal toxins•  It is contagious and can be transmitted through contact or

consumption of infected meat• Anthrax does not spread directly from one infected animal or

person to another; rather, it is spread by spores. These spores can be transported by clothing or shoes• B. anthracis bacterial spores are soil-borne. Because of their

long lifespan, spores are present globally and remain at the burial sites of animals killed by anthrax for many decades. Disturbed grave sites of infected animals have caused reinfection over 70 years after the animal's interment

Diagnosis• Gram staining : rod shaped, gram positive,broad

• Anthrax quick ELISA test – New test approved by FDA on June 7th, 2004. – Detects antibodies to Protective Antigen of B.Anthracis – Quicker and easier to interpret than previous antibody testing methods • Results in less than one hour

• From clinical samples, such as blood, cerebrospinal fluid (CSF), skin lesion (eschar), or oropharyngeal ulcer

– Encapsulated gram-positive rods on Gram stain

• From growth on sheep blood agar: – Large gram-positive rods – Nonmotile– Nonhemolytic

• Culture and identification of B.AnthracisAerobe, facultative anaerobe Grows between 12 -45 c 2-3 mm colonies Edge like matted hair Medusa head appearance Blood agar Hemolytic coloniesString of pearl appearance withpenicillin

• Gelatin stab culture Inverted fir tree appearance

• Chest X-raywidened mediastinum, pleural effusions, infiltrates, pulmonary

congestion

• Ascoli testa precipitin test for anthrax using a tissue extract and anthrax

 antiserum

• PCR testPCR only takes several hoursRapid cycle RT-PCR can be done in 1-2 hoursWith PCR confirmation can start the treatment early