Updated: 12/23/2021

Anthrax

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  • Snapshot
    • A 40-year-old farmer from rural China presents to a local hospital for fever and cough. He reports to have had a nonproductive cough for a few days and feels more short of breath and lightheaded this morning. He works frequently with sheep on the countryside. On physical exam, his temperature is 102.2°F (39.0°C), blood pressure is 100/70 mm Hg, pulse is 96/min, and respirations are 22/min. On physical exam, there is bilateral rhonchi in the lung bases. Chest radiograph reveals a widened mediastinum and bilateral infiltrates.
  • Introduction
    • Classification
      • Bacillus anthracis
        • spore-forming and exotoxin-forming gram + rod
        • capsule protects against phagocytosis
          • the only bacterial with polypeptide capsule (poly-D-glutamate)
      • transmission
        • inhalation of spores
        • direct contact of spores to a skin break
        • ingestion of spores
    • Associated conditions
      • cutaneous anthrax
        • most common
      • pulmonary anthrax
        • “woolsorter’s disease”
      • gastrointestinal anthrax
    • Prevention
      • post-exposure prophylaxis
        • 3 doses of anthrax vaccine
        • 60 days of a single antibiotic
          • ciprofloxacin or doxycycline are first line
  • Epidemiology
    • Incidence
      • more common in areas where animal vaccination rates are low
      • bioterrorism
    • Risk factors
      • intravenous drug use (e.g., heroin)
      • occupational exposure to unvaccinated animals
      • occupational exposure to animal hides
  • ETIOLOGY
    • Pathogenesis
      • edema toxin performs the same function as adenylate cyclase, ↑ cAMP and results in
        • black eschar with edematous borders
        • vasodilation and hypotension
      • infection may spread via lymphatics
  • Presentation
    • Symptoms
      • pulmonary anthrax
        • flu-like syndrome with non-productive cough
        • nausea and vomiting
        • hemoptysis
        • chest pain
      • gastrointestinal anthrax
        • nausea and vomiting
        • dysentery
        • abdominal pain
    • Physical exam
      • cutaneous anthrax
        • initial lesion is a painless and pruritic papule with central vesicle or bulla
        • this progresses to painless and necrotic black eschar
          • surrounded by edema
        • eschar sloughs off at day 14
      • pulmonary anthrax
        • mediastinitis
        • shock
        • hypoxia
        • dyspnea
      • lymphadenopathy
  • Imaging
    • Chest radiography
      • indication
        • pulmonary anthrax
      • findings
        • pleural effusion
        • pulmonary consolidation
        • widened mediastinum
  • Studies
    • Labs
      • multiple methods of detection
        • “medusa head” appearance on microscopy
          • halo of projections
        • culture of blood, pleural fluid, or eschar
        • positive Gram stain of affected tissue
          • box-car like appearance
        • polymerase chain reaction
        • anti-protective antigen immunoglobulin G on enzyme-linked immunosorbent assay
        • biopsy with immunohistochemistry staining
      • marked hemoconcentration
    • Making the diagnosis
      • most cases are diagnosed clinically and confirmed with
        • positive culture, serology, or immunohistochemistry
        • detection of Bacillus anthracis DNA in tissue
  • Differential
    • Community-acquired pneumonia
      • distinguishing factor
        • less likely to have nausea, vomiting, pallor, or unexplained mediastinal widening on chest radiography
  • Treatment
    • Management approach
      • antibiotics should be given in the prodromal phase of the disease
      • cutaneous anthrax can be treated with 1 antibiotic
      • systemic anthrax can be treated with 2 antibiotics
    • Medical
      • ciprofloxacin or doxycycline
        • indication
          • all patients
        • doxycycline adverse effects
          • gastrointestinal upset, photosensitivity, teeth discoloration, and inhibition of bone growth in children
          • photosensitivity
        • ciprofloxacin adverse effects
          • gastrointestinal upset, risk of tendon rupture, and QT prolongation
      • protein synthesis inhibitor
        • indications
          • systemic anthrax
          • combination therapy with fluoroquinolone or doxycycline
        • mechanism
          • reduces toxin production
        • drugs
          • clindamycin
          • linezolid
      • antitoxins
        • indication
          • all patients
        • drugs
          • monoclonal antibodies
            • raxibacumab
          • anthrax immunoglobulin
  • Complications
    • Bacteremia from cutaneous anthrax
    • Death
  • Prognosis
    • Biphasic nature of pulmonary anthrax
      • prodromal symptoms
      • fulminant bactermic phase
        • often leads to death within days
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