Anthrax Diagnostic Testing Recommendations by Specimen Type

Lesion Swabs - Cutaneous

Specimen Collection and Processing

The specific location of swab sampling will depend on the stage of the lesion.

Note: Regardless of the stage of the lesion, collect 2 separate swabs. One swab will be for culture, and the second swab will be for real-time polymerase chain reaction (PCR).

Vesicular Stage

  • Aseptically collect vesicular fluid on sterile dry swabs from previously unopened vesicles

Eschar Stage – collect the eschar material by:

  • Carefully lift the eschar’s outer edge
  • Insert a sterile moist swab (pre-moistened with sterile saline).
  • Rotate the swab slowly for 2-3 seconds beneath the edge of the eschar before removing it.

Ulcer – if no vesicle or eschar is present:

  • Swab the base of the ulcer using a sterile moist swab (pre-moistened with sterile saline).
Specimen Submission
  • For samples intended for culture OR both culture and real-time PCR:
    • Ship using cold packs and store at 2-8°C
  • For samples intended for real-time PCR testing only:
    • Ship on dry ice and store at -70°C

Lesion Swabs - Gastrointestinal

Specimen Collection and Processing

The specific location of swab sampling will depend on the type of the patient’s lesion(s).

Note: Regardless of the stage of the lesion, collect 2 separate swabs. One swab will be for culture, and the second swab will be for real-time polymerase chain reaction (PCR).

Oropharyngeal

  • Use a sterile moist swab (pre-moistened with sterile saline) to aseptically swab the surface and edge of suspected lesions. Lesions may be present:
    • In the oropharynx or buccal cavity.
    • On the tongue, tonsils, or posterior pharyngeal wall.

Intestinal

  • Use a sterile dry swab to collect a rectal swab.
Specimen Submission
  • For culture OR both culture and real-time PCR:
    • Ship using cold packs and store at 2-8°C
  • For real-time PCR testing only:
    • Ship on dry ice and store at -70°C

Biopsy - Cutaneous

Specimen Collection and Processing

A skin biopsy should be taken for all patients with a lesion being tested for cutaneous anthrax, preferably before the patient has started antibiotic treatment. Biopsies should be taken from both the vesicle and eschar, if present.

  • If the patient has not started antibiotics OR antibiotics have been started within 24 hours:
    • Take a full thickness punch biopsy specimen for culture and real-time PCR, and
    • Take one full thickness punch biopsy sample from the papule or vesicle (include adjacent skin) for histopathology, special stains, and IHC.
  • If the patient is on antibiotics at the time of presentation:
    • Take one full thickness punch biopsy sample from the papule or vesicle (include adjacent skin) for histopathology, special stains, and IHC.
    • Place the sample into 10% buffered formalin for fixation. Do not freeze.
Specimen Submission
  • If the samples are formalin-fixed, ship to CDC at room temperature. Do not freeze.
  • If the specimen is fresh-frozen, store at -70°C and ship to CDC using dry ice.
  • Biopsy specimens should be accompanied by supporting documents, including:
    • A brief clinical history and description of the lesion.
    • A chronology of the presentation of the lesion(s).
    • A description of the treatment course (with duration and dosage).
    • The date of biopsy in relation to the initiation of antibiotic treatment.
    • A photograph, digital image, or diagram of the biopsy sites.

For additional instructions on pathology testing, visit the Infectious Diseases Pathology Branch website.

Biopsy - Injection

Specimen Collection and Processing

Tissue samples can be obtained for patients with symptoms of injection anthrax during lesion debridement procedures or surgical interventions.

Specimen Submission
  • If the samples are formalin-fixed, ship to CDC at room temperature. Do not freeze.
  • If the specimen is fresh-frozen, store at -70°C and ship to CDC using dry ice.
  • Biopsy specimens should be accompanied by supporting documents, including:
    • A brief clinical history and description of the lesion.
    • A chronology of the presentation of the lesion(s).
    • A description of the treatment course (with duration and dosage).
    • The date of biopsy in relation to the initiation of antibiotic treatment.
    • A photograph, digital image, or diagram of the biopsy sites.

For additional instructions on pathology testing, visit the Infectious Diseases Pathology Branch website.

Biopsy - Inhalation

Specimen Collection and Processing

A bronchial or pleural biopsy can be obtained for patients with symptoms of inhalation anthrax.

Specimen Submission
  • If the samples are formalin-fixed, ship to CDC at room temperature. Do not freeze.
  • If the specimen is fresh-frozen, store at -70°C and ship to CDC using dry ice.
  • Biopsy specimens should be accompanied by supporting documents, including:
    • A brief clinical history and description of the lesion.
    • A chronology of the presentation of the lesion(s).
    • A description of the treatment course (with duration and dosage).
    • The date of biopsy in relation to the initiation of antibiotic treatment.
    • A photograph, digital image, or diagram of the biopsy sites.

For additional instructions on pathology testing, visit the Infectious Diseases Pathology Branch website.

Serum - Cutaneous, Gastrointestinal, Inhalation, Injection and Meningeal

Serum testing can be used to determine if the body has developed an immune response to anthrax.

Serology Testing

Serum samples for serological testing should be sent in pairs, including:

  • An acute serum specimen (≤7 days after symptom onset OR as soon as possible after a known exposure event)
    AND
  • A convalescent-phase (14–35 days after symptom onset) specimen. It is recommended that the convalescent-phase specimen be taken 2 weeks after the acute specimen.
Lethal Factor (LF) Toxin Testing

Specimens for lethal factor (LF) testing may be collected from 0 to 18 days after suspected exposure or the onset of symptoms. Earlier is preferred because of gradual declines in toxin levels during antimicrobial therapy.

Collecting, Preparing, and Shipping Serum Specimens

Plasma - Cutaneous, Gastrointestinal, Inhalation, Injection and Meningeal

Plasma testing can be used to determine if anthrax lethal factor toxins are present in the body.

Specimen Collection and Processing

Specimens for lethal factor toxin testing may be collected from 0 to 18 days after suspected exposure or the onset of symptoms. Earlier is preferred because of gradual declines in toxin levels during antimicrobial therapy.

  • Collect 10 mL using EDTA purple top tube.
  • Keep the specimen on ice for 30 minutes, then centrifuge.
Specimen Submission

Ship specimens using dry ice.

Blood - Cutaneous, Gastrointestinal, Inhalation, Injection and Meningeal

Specimen Collection and Processing

Blood Culture

  • Collect specimens prior to starting antimicrobial therapy.
  • Collect the blood volume and number of sets as instructed by hospital laboratory protocol.
  • Note: for Cutaneous Anthrax: Collect specimen for blood culture if the patient shows signs of systemic infection.

Real-time polymerase chain reaction (PCR)

  • Collect 10 mL blood in EDTA or Sodium Citrate (purple or blue top tubes). For pediatric cases, collect volumes allowable.
Specimen Submission

Ship specimens for blood culture and real-time PCR using cold packs.

Pleural Fluid - Inhalation

Specimen Collection and Processing
  • Collect > 1 mL of pleural fluid into a sterile container for culture, real-time polymerase chain reaction (PCR), and anthrax lethal factor toxin testing
  • Pleural fluid specimens should be stored at 2-8°C for no more than 24 hours
Specimen Submission

Ship specimens using cold packs.

Cerebrospinal Fluid (CSF) – Meningeal

Specimen Collection and Processing

Collect > 1mL of CSF into a sterile container for culture and real-time polymerase chain reaction (PCR)

Specimen Submission

Ship specimens using cold packs.

Ascites Fluid - Gastrointestinal

Specimen Collection and Processing
  • Collect the appropriate volume of ascites fluid, according to local hospital protocol, for culture, real-time polymerase chain reaction (PCR), and anthrax lethal factor toxin testing
  • Specimen should be collected prior to starting antimicrobial therapy

Autopsy Tissues - Inhalation

Specimen Collection and Processing
  • It is preferable to submit a minimum of 8 blocks and fixed tissue representing different pulmonary sites for histopathology, special stains, and IHC, such as:
    • Hilar lung with regional lymph nodes, bronchi, and trachea.
    • Peripheral pulmonary parenchyma from both lungs.
  • Representative portions from all major organs (lung, heart, liver, kidney, spleen, and brain), particularly those organs showing significant gross or microscopic pathology.
Specimen Submission

Paraffin-embedded tissue blocks (preferred specimen)

  • It is important to submit tissue blocks before tissues have been in formalin for a significant time. Prolonged fixation (>2 weeks) may interfere with some IHC and molecular diagnostic assays.

Wet tissue

  • It is recommended that unprocessed tissues in 10% neutral buffered formalin be submitted IN ADDITION to paraffin blocks.
  • Do not freeze formalin-fixed samples.

Autopsy tissue specimens should be accompanied by supporting documentation, including:

  • A completed CDC 50.34 formCdc-pdfpdf icon pdf icon[PDF – 593KB]
  • A cover letter outlining a brief clinical history, including relevant demographic/epidemiologic information
  • A copy of (a) the autopsy report (preliminary or final) or (b) surgical pathology report
  • Copies of laboratory results (microbiology, hematology, serology, culture, and/or biochemical)
  • A description of the treatment course (with duration and dosage)
  • Images (clinical and/or gross autopsy photos)

For instructions on autopsy testing, visit the Infectious Diseases Pathology Branch website.

Autopsy Tissues - Fatal Cutaneous, Gastrointestinal, Injection and Meningeal

Specimen Collection and Processing

Preferred specimens for histopathology, special stains, and IHC. include:

  • Paraffin blocks of tissues showing gross or microscopic pathology and representative tissues in formalin (such as areas of the gastrointestinal tract that show gross findings).
  • Representative portions from all major organs (lung, heart, liver, kidney, spleen, and brain), particularly those organs showing significant gross or microscopic pathology
Specimen Submission

Paraffin-embedded tissue blocks (preferred specimen)

  • It is important to submit tissue blocks before tissues have been in formalin for a significant time. Prolonged fixation (>2 weeks) may interfere with some IHC and molecular diagnostic assays.

Wet tissue

  • It is recommended that unprocessed tissues in 10% neutral buffered formalin be submitted IN ADDITION to paraffin blocks.
  • Do not freeze formalin-fixed samples.

Autopsy tissue specimens should be accompanied by supporting documentation, including:

  • A completed CDC 50.34 formCdc-pdfpdf icon pdf icon[PDF – 593KB]
  • A cover letter outlining a brief clinical history, including relevant demographic/epidemiologic information
  • A copy of (a) the autopsy report (preliminary or final) or (b) surgical pathology report
  • Copies of laboratory results (microbiology, hematology, serology, culture, and/or biochemical)
  • A description of the treatment course (with duration and dosage)
  • Images (clinical and/or gross autopsy photos)

For instructions on autopsy testing, visit the Infectious Diseases Pathology Branch website.