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How is
anthrax diagnosed?
Anthrax is diagnosed by isolating B. anthracis from the blood,
skin lesions, or respiratory secretions or by measuring specific antibodies
in the blood of persons with suspected cases.
In patients
with symptoms compatible with anthrax, providers should confirm the diagnosis
by obtaining the appropriate laboratory specimens based on the clinical
form of anthrax that is suspected (i.e., cutaneous, inhalational, or gastrointestinal).
Cutaneous
- vesicular fluid and blood
Inhalational - blood, cerebrospinal fluid (if meningeal signs are present)
or chest X-ray
Gastrointestinal - blood
For more
information, read Update:
Investigation of Bioterrorism-Related Anthrax and Interim Guidelines for
Clinical Evaluation of Persons with Possible Anthrax.
What
are the standard diagnostic tests used by the laboratories?
Presumptive identification to identify to genus level (Bacillus
family of organisms) requires Gram stain and colony identification.
Presumptive
identification to identify to species level (B. anthracis) requires
tests for motility, lysis by gamma phage, capsule production and visualization,
hemolysis, wet mount and malachite green staining for spores.
Confirmatory
identification of B. anthracis carried out by CDC may include phage
lysis, capsular staining, and direct fluorescent antibody (DFA) testing
on capsule antigen and cell wall polysaccharide.
When
is a nasal swab indicated?
Nasal swabs and screening may assist in epidemiologic investigations,
but should not be relied upon as a guide for prophylaxis or treatment.
Epidemiologic investigation in response to threats of exposure to B.
anthracis may employ nasal swabs of potentially exposed persons as
an adjunct to environmental sampling to determine the extent of exposure.
Why were
nasal swabs used to screen individuals in the Florida investigation for
anthrax?
The nasal swab test was used as a screening tool because, following initial
recognition of the case of confirmed inhalational anthrax, there were
no known sources of exposure. Determining whether anyone else associated
with the case-patient might have been exposed was important. In this setting,
the nasal swab method was used for a rapid assessment of exposure among
people, and as a tool for rapid environmental assessment. When the source
of exposure is not known, nasal swabs can help investigators determine
that information. They are not used for diagnosing people with anthrax,
and they are not 100 percent effective in determining all who may have
been exposed. See also http://www.bt.cdc.gov/documentsapp/faqanthrax.asp#Q602.
Is there
an X-ray for detecting anthrax?
A chest X-ray can be used to help diagnose inhalation anthrax in people
who have symptoms. It is not useful as a test for determining anthrax
exposure or for people with no symptoms.
Can someone
get anthrax from contaminated mail, equipment or clothing?
In the mail handling processing sites, B. anthracis spores may
be aerosolized during the operation and maintenance of high-speed, mail
sorting machines potentially exposing workers. In addition, these spores
could get into heating, ventilating, or air conditioning (HVAC) systems.
CDC interim guidelines have been issued to advise workers on how best
to protect themselves in the workplace.
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