Anthrax Diagnostic Testing Recommendations by Specimen Type

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 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 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 Collection and Processing

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

Specimen Collection and Processing

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

Collecting, Preparing, and Shipping Serum Specimens

• Follow CDC’s instruction to collect, prepare and ship serum.
• Process serum specimen using Biosafety Level (BSL) 2 practices. (see Biosafety in Microbiological and Biological Laboratories).
• DO NOT send blood culture bottles or whole blood.

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 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 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 Collection and Processing

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

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

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 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