Cutaneous Anthrax: Recommended Specimens for Microbiology and Pathology for Diagnosis
Specimens should be collected from any patient being evaluated for cutaneous Bacillus anthracis infection. We recommend that the following specimens be collected for cutaneous anthrax testing.
- Swabs of Lesion:
- Regardless of the stage of the lesion, collect 2 separate swabs
- 1 swab for Gram stain and culture
- 1 swab for Polymerase Chain Reaction (PCR)
- The specific location/sampling of the swab would depend on the stage of the lesion
- Vesicular stage: Aseptically collect vesicular fluid on sterile dry swabs from previously unopened vesicles. Note: Anthrax bacilli are most likely to be seen by Gram stain in the vesicular stage.
- Eschar stage: Collect eschar material by carefully lifting the eschar’s outer edge; insert a sterile dry swab, then slowly rotate for 2-3 seconds beneath the edge of the eschar without removing it.
- Ulcer: If no vesicle or eschar is present, swab the base of the ulcer using a moist swab (pre-moistened with sterile saline).
- Specimens intended for culture, or both culture and PCR should be shipped using cold packs and stored at 2 to 8°C; specimens intended for PCR testing only may be shipped on dry ice and stored at -70°C.
- Regardless of the stage of the lesion, collect 2 separate swabs
- Biopsy
- A skin biopsy should be obtained on every patient with a lesion being evaluated for cutaneous anthrax.
- If the patient is on antimicrobial therapy at the time of presentation, obtain one full thickness punch biopsy sample from papule or vesicle and include adjacent skin; place into 10% buffered formalin for histopathology and immunohistochemistry (IHC).
- If the patient is not yet receiving antibiotics or if antibiotic therapy has been initiated in the proceeding 24 hours, obtain a second full thickness punch biopsy specimen for culture, Gram stain, PCR and frozen tissue IHC.
- Do not attempt to split one sample for items 2 and 3 above, separate samples should be obtained.
- Biopsies should be taken from both vesicle and eschar, if present.
More specific guidelines on collection of these specimens are provided in Shieh et al. American Journal of Pathology, Nov 2003, Vol 163, No. 5, Page 1908, Column 2.
- Fresh samples (not formalin fixed) should be stored and shipped frozen to CDC at -70°C; formalin fixed samples should be shipped at room temperature.
- A skin biopsy should be obtained on every patient with a lesion being evaluated for cutaneous anthrax.
- Serum (process using BSL2 practices)
- Acute serum specimens should ALWAYS be collected within the first 7 days of symptom onset or as soon as possible after known exposure.
- Even if diagnosis of anthrax is confirmed by isolation of B. anthracis from clinical specimens, collect a convalescent serum sample, 14-35 days after symptom onset.
- Both acute and convalescent serum specimens should be obtained from a minimum of 8 mls blood, yielding ~ 4 mls of sera (laboratories may be testing for multiple potential etiologies).
- Separate serum from clot; sera should frozen immediately following separation and stored frozen at -20°C or colder, and should be shipped frozen on dry ice to CDC, in appropriately labeled plastic screw cap vials.
- Do NOT send blood culture bottles or whole blood.
- Appropriate use of the commercially available Immunetics QuickELISA™ Anthrax-PA Kit:
- The Immunetics Kit should be considered a primary screening serology test
- This test generates a positive /negative result; therefore any paired sera producing either a
- -/+ reaction (acute/convalescent) or
- +/+ reaction
should be sent to CDC for confirmation and quantitative ELISA measurements.
- -/- reaction (acute/convalescent) or
- +/- reaction
do not need confirmation.
- Blood
- If the patient has evidence of systemic symptoms, specimens for blood culture should be obtained. Collect appropriate blood volume and number of sets per local hospital laboratory protocol.
- Collect 10 ml blood in EDTA (purple top tubes) for PCR
- Page last updated February 22, 2006
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