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
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.Anthracis
Aerobe, facultative anaerobe
Grows between 12 -45 c
2-3 mm colonies
Edge like matted hair
Medusa head appearance
Blood agar Hemolytic colonies
String of pearl appearance with
penicillin
• Gelatin stab culture
Inverted fir tree appearance
• Chest X-ray
widened mediastinum, pleural effusions, infiltrates, pulmonary congestion
• Ascoli test
a precipitin test for anthrax using a tissue extract and anthrax antiserum
• PCR test
PCR only takes several hours
Rapid cycle RT-PCR can be done in 1-2 hours
With PCR confirmation can start the treatment early