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CBRNE - Anthrax Infection: Differential Diagnoses & Workup

Author: Hilarie Cranmer, MD, MPH, FACEP, Director, Global Women's Health Fellowship, Associate Director, Harvard International Emergency Medicine Fellowship, Department of Emergency Medicine, Brigham and Women's Hospital; Director, Humanitarian Studies Program, Harvard Humanitarian Initiative; Assistant Professor, Harvard University School of Medicine
Coauthor(s): Mauricio Martinez, MD, Assistant Medical Director, Department of Emergency Medicine, Winchester Medical Center
Contributor Information and Disclosures

Updated: Oct 26, 2009

Differential Diagnoses

Aneurysm, Abdominal
Pleural Effusion
CBRNE - Plague
Pneumonia, Bacterial
Coccidioidomycosis
Pneumonia, Mycoplasma
Diphtheria
Pneumonia, Viral
Dissection, Aortic
Subarachnoid Hemorrhage
Gastroenteritis
Superior Vena Cava Syndrome
Meningitis

Other Problems to Be Considered

Ecthyma (Pseudomonas aeruginosa and staphylococcal infections)
Glanders (Pseudomonas pseudomallei)
Histoplasmosis
Leprosy
Orf (Rickettsia akari)
Psittacosis
Rat bite fever (Streptococcus moniliformis, Spirillum minus)
Rickettsia
Tularemia
Typhoid

Workup

Laboratory Studies

  • Blood culture and Gram stain are high yield tests in infected persons who have not taken antibiotics. Sputum from patients seldom yields positive smears or cultures. A Gram stain is the easiest means of initially identifying suggested cases. Anthrax appears as a large, gram-positive rod. In October 2001, blood cultures were positive for anthrax in all 8 patients who did not receive antibiotics. Serologic diagnosis of anthrax can be made using a microhemagglutination test specific for the protective antigen (PA) component of the toxin. Any Gram stain results suggestive of anthrax should be reported to the CDC.
  • Several biochemical tests aid in differentiating B anthracis from other members of the species (chief among them is Bacillus cereus, which has been associated with outbreaks of human food poisoning). B anthracis is characterized by the absence of hemolysis on sheep blood agar, lack of motility, absence of salicin fermentation, gelatin hydrolysis, and lack of growth on phenylethyl alcohol medium.
  • Cerebral spinal fluid contains blood and leukocytosis in meningeal anthrax.
  • An enzyme-linked immunosorbent assay (ELISA) to detect immunoglobulin G (IgG) response to B anthracis protective antigen (PA) is 98.6% sensitive and 80% specific. PA–competitive inhibition ELISA is used as a second confirmatory step to improve specificity. Specific IgG anti-PA antibody can be detected as early as 10 days after onset of symptoms, but peak IgG levels may not be observed until 40 days of symptom onset.
  • In persons exposed to antibiotics, immunohistochemical examination of the suspected fluid (eg pleural fluid, cerebrospinal fluid [CSF], cutaneous biopsy) using antibodies to B anthracis cell wall and capsule is performed.

Imaging Studies

  • Chest radiography: Inhalational anthrax often does not appear on chest radiographs as a typical pneumonia; therefore, pulmonary densities often are absent. A prominent mediastinum with pleural effusions may be present. The prominent mediastinum is caused by hilar lymphadenopathy. An absence of parenchymal involvement exists. In the 11 cases of inhalational anthrax, initial examination was often subtle but showed mediastinal widening, paratracheal and hilar fullness, and pleural effusions and/or infiltrates.


Anthrax infection. Inhalation anthrax. Chest radi...

Anthrax infection. Inhalation anthrax. Chest radiograph with widened mediastinum 22 hours before death. Image courtesy of Dr P.S. Brachman, Public Health Image Library, CDC, Atlanta, Ga.

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Anthrax infection. Inhalation anthrax. Chest radi...

Anthrax infection. Inhalation anthrax. Chest radiograph with widened mediastinum 22 hours before death. Image courtesy of Dr P.S. Brachman, Public Health Image Library, CDC, Atlanta, Ga.

  • Computed tomography (CT) of the chest: CT scan of the chest detects hemorrhagic mediastinal and hilar lymph nodes and edema, peribronchial thickening, and pleural effusions. It also may help differentiate from histoplasmosis, sarcoidosis, tuberculosis, and lymphoma.

More on CBRNE - Anthrax Infection

Overview: CBRNE - Anthrax Infection
Differential Diagnoses & Workup: CBRNE - Anthrax Infection
Treatment & Medication: CBRNE - Anthrax Infection
Follow-up: CBRNE - Anthrax Infection
Multimedia: CBRNE - Anthrax Infection
References
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References

  1. Inglesby TV, O'Toole T, Henderson DA, Bartlett JG, Ascher MS, Eitzen E. Anthrax as a biological weapon, 2002: updated recommendations for management. JAMA. May 1 2002;287(17):2236-52. [Medline].

  2. Food and Drug Administration. 17.5 FDA-Approved Medication Guide. Levaquin (levofloxacin). Accessed August 6, 2009. [Full Text].

  3. CDC. Vaccines and Preventable Diseases:Anthrax Vaccination. Vaccines:VPF-VAD/Anthrax/mainpage. Available at http://www.cdc.gov/vaccines/vpd-vac/anthrax/default.htm#vacc. Accessed July 9, 2009.

  4. Abramova FA, Grinberg LM, Yampolskaya OV, Walker DH. Pathology of inhalational anthrax in 42 cases from the Sverdlovsk outbreak of 1979. Proc Natl Acad Sci U S A. Mar 15 1993;90(6):2291-4. [Medline].

  5. Bell DM, Kozarsky PE, Stephens DS. Clinical issues in the prophylaxis, diagnosis, and treatment of anthrax. Emerg Infect Dis. Feb 2002;8(2):222-5. [Medline].

  6. CDC. Centers for Disease Control and Prevention Anthrax Fact Sheets & Overviews. CDC Anthrax Fact Sheets & Overviews. Available at http://www.bt.cdc.gov/agent/anthrax/basics/factsheets.asp. Accessed July 9, 2009.

  7. Dixon TC, Meselson M, Guillemin J, Hanna PC. Anthrax. N Engl J Med. Sep 9 1999;341(11):815-26. [Medline].

  8. Fennelly KP, Davidow AL, Miller SL, et al. Airborne infection with Bacillus anthracis--from mills to mail. Emerg Infect Dis. Jun 2004;10(6):996-1002. [Medline]. [Full Text].

  9. Shepard CW, Soriano-Gabarro M, Zell ER, et al. Antimicrobial postexposure prophylaxis for anthrax: adverse events and adherence. Emerg Infect Dis. Oct 2002;8(10):1124-32. [Medline].

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Further Reading

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Keywords

anthrax, Bacillus anthracis, , black bane, the fifth plague, wool-sorter's disease, woolsorter's disease, anthrax infection, inhalation anthrax, cutaneous anthrax, GI anthrax, gastrointestinal anthrax, oropharyngeal anthrax, meningeal anthrax, postexposure prophylaxis, PEP, biologic warfare agent, influenzalike illness, malignantpustules, black eschar

acute respiratory distress, hypoxemia, cyanosis, hypothermia, shock, enlarged mediastinal lymph nodes, subarachnoid hemorrhage, pleural effusions, meningismus, ileus, GI hemorrhage, dysphagia, oral bleeding,biological weapon, biological terrorism, biological warfare, biowarfare

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Contributor Information and Disclosures

Author

Hilarie Cranmer, MD, MPH, FACEP, Director, Global Women's Health Fellowship, Associate Director, Harvard International Emergency Medicine Fellowship, Department of Emergency Medicine, Brigham and Women's Hospital; Director, Humanitarian Studies Program, Harvard Humanitarian Initiative; Assistant Professor, Harvard University School of Medicine
Hilarie Cranmer, MD, MPH, FACEP is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, Massachusetts Medical Society, Physicians for Human Rights, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Coauthor(s)

Mauricio Martinez, MD, Assistant Medical Director, Department of Emergency Medicine, Winchester Medical Center
Mauricio Martinez, MD is a member of the following medical societies: American Academy of Emergency Medicine
Disclosure: Nothing to disclose.

Medical Editor

James Li, MD, Former Assistant Professor, Division of Emergency Medicine, Harvard Medical School; Board of Directors, Remote Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Barry J Sheridan, DO, Chief, Department of Emergency Medical Services, Brooke Army Medical Center
Barry J Sheridan, DO is a member of the following medical societies: American Academy of Emergency Medicine
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Robert G Darling, MD, FACEP, Clinical Assistant Professor of Military and Emergency Medicine, Uniformed Services University of the Health Sciences, F Edward Hebert School of Medicine; Associate Director, Center for Disaster and Humanitarian Assistance Medicine
Robert G Darling, MD, FACEP is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, and Association of Military Surgeons of the US
Disclosure: Nothing to disclose.

 
 
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