Recommended Specimens for Anthrax Testing by Clinical Presentation

Recommended specimens by clinical presentation

Culturing B. anthracis from clinical specimens is the gold standard for diagnosing anthrax. If anthrax is suspected, clinical specimens, including blood cultures, should be collected before starting antimicrobial therapy. Culture will likely be negative if clinical specimens are collected after initiating antimicrobial therapy, regardless of the form of disease (cutaneous, gastrointestinal, inhalation, injection, or meningeal anthrax). However, other tests not requiring a viable organism may be positive after antimicrobial use, if collected as directed below.

Depending on the form of disease, organisms can be cultured from the following specimens:

  • Blood
  • Skin lesion exudates
  • Pleural fluid
  • Cerebrospinal fluid (CSF)
  • Rectal swab
  • Ascites fluid
  • Tissues from biopsy or autopsy

Each section contains guidance for recommended biological specimens that may be submitted for anthrax diagnostic testing. Note: On a case-by-case basis, one or more clinical specimens may be recommended for submission, as available.

Specific packaging and shipping information by specimen and test type:

Cutaneous

Lesion Swabs

Vesicular lesions: Two swabs of vesicular fluid from an unopened vesicle, one for culture and one for real-time polymerase chain reaction (PCR).

Eschars: Two saline-moistened swab samples, rotated underneath the eschar, one for culture and one for real-time PCR.

Ulcers: Sample the base of the lesion with two saline-moistened swabs, one for culture and one for real-time PCR.

Biopsy

A full thickness biopsy of a papule or vesicle, including adjacent skin, for histopathology, special stains, and immunohistochemistry (IHC).

Note: For patients who are not on antibiotic therapy or who have been on therapy for < 24 hours, a second biopsy sample should be collected at the same time and submitted for culture and real-time PCR.

Serum

An acute (≤7 days after symptom onset OR as soon as possible after a known exposure event) serum sample to test for anthrax lethal factor toxin.

Acute and convalescent (14–35 days after symptom onset) serum samples for serologic testing.

Plasma

An acute plasma sample to test for anthrax lethal factor toxin.

Note: Plasma is the preferred specimen for anthrax lethal factor toxin testing.

Blood

If there are signs of systemic anthrax infection (i.e., febrile or hypothermia, tachycardia, tachypnea, hypotensive), collect blood specimen before starting antimicrobial therapy for culture and real-time PCR.

CSF

To be submitted for patients with severe headache, meningeal signs, altered mental status, seizures, or focal signs for culture and real-time PCR.

Autopsy Tissues

To be collected in fatal cases for histopathology, special stains, and IHC.

Gastrointestinal

Oropharyngeal lesion swab, if present

To be tested for culture and real-time PCR.

Serum

An acute (≤7 days after symptom onset OR as soon as possible after a known exposure event) serum sample to test for anthrax lethal factor toxin.

Acute and convalescent (14–35 days after symptom onset) serum samples for serologic testing.

Plasma

Acute plasma samples for testing of anthrax lethal factor toxin.

Note: Plasma is the preferred specimen for anthrax lethal factor toxin testing.

Blood

To be drawn before starting antimicrobial therapy for culture and real-time PCR.

Ascites Fluid

To be tested for culture, real-time PCR, and anthrax lethal factor toxin testing.

Rectal swab

To be tested for culture and real-time PCR.

Autopsy Tissues

To be collected in fatal cases for histopathology, special stains, and IHC.

Inhalation

Serum

An acute (≤7 days after symptom onset OR as soon as possible after a known exposure event) serum sample to test for anthrax lethal factor toxin.

Acute and convalescent (14–35 days after symptom onset) serum samples for serologic testing.

Plasma

An acute plasma sample to test for anthrax lethal factor toxin.

Note: Plasma is the preferred specimen for anthrax lethal factor toxin testing.

Blood

To be drawn before starting antimicrobial therapy for culture and real-time PCR.

Pleural Fluid

To be tested for culture and real-time PCR, as well as anthrax lethal factor toxin.

CSF

To be submitted for patients with severe headache, meningeal signs, altered mental status, seizures, or focal signs for culture and real-time PCR.

Biopsy

Pleural and/or bronchial biopsies for IHC.

Autopsy Tissues

To be collected in fatal cases for histopathology, special stains, and IHC.

Injection

Serum

An acute (≤7 days after symptom onset OR as soon as possible after a known exposure event) serum sample to test for anthrax lethal factor toxin.

Acute and convalescent (14–35 days after symptom onset) serum samples for serologic testing.

Plasma

An acute plasma sample to test for anthrax lethal factor toxin.

Note: Plasma is the preferred specimen for anthrax lethal factor toxin testing.

Blood

To be drawn before starting antimicrobial therapy for culture and real-time PCR.

Biopsy

Tissue biopsy from localized lesion tissue debridement.

Autopsy Tissues

To be collected in fatal cases for histopathology, special stains, and IHC.

Meningeal

Meningitis can complicate cases of cutaneous, gastrointestinal, inhalation, and injection anthrax cases. Meningitis may also be the primary sign of anthrax in patients without a clear source of exposure. The following specimens should be submitted in patients with severe headaches, meningeal signs, altered mental status, seizures, or focal signs.

Serum

An acute (≤7 days after symptom onset OR as soon as possible after a known exposure event) serum sample to test for anthrax lethal factor toxin.

Acute and convalescent (14–35 days after symptom onset) serum samples for serologic testing.

Plasma

An acute plasma sample to test for anthrax lethal factor toxin.

Note: Plasma is the preferred specimen for anthrax lethal factor toxin testing.

Blood

To be drawn before starting antimicrobial therapy for culture and real-time PCR.

CSF

To be tested for culture and real-time PCR.

Autopsy Tissues

To be collected in fatal cases for histopathology, special stains, and IHC.