Anthrax
Anthrax is caused by Bacillus anthracis spores acquired by inhalation, cutaneous inoculation, or ingestion, with cutaneous disease most common and inhalational disease most lethal. Systemic disease is treated with ciprofloxacin or doxycycline plus additional agents and antitoxin for 60 days, and any inhalational case is a bioterrorism sentinel event requiring immediate public health notification.
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What this article covers
- Overview
Bacillus anthracis infection: a spore-forming, gram-positive, "box-car"-shaped bacillus that produces disease through three clinical forms: cutaneous (most common), inhalational (most deadly), and gastrointestinal.
- Epidemiology
Occupational cluster pattern: naturally occurring cases cluster among individuals handling livestock or animal products (wool-sorters, tanners, farmers, veterinarians); a temporal or demographic…
- Risk factors
Direct animal or animal-product contact: handling infected livestock, hides, wool, hair, or bone meal.
- Pathophysiology
Spore germination at the site of entry: B.
- Clinical features
Cutaneous anthrax (most common): begins 1-7 days after skin exposure as a painless-to-pruritic papule that enlarges into an ulcer with a surrounding edematous halo and a round, raised, regular…
- Differential diagnosis
Plague (Yersinia pestis): fulminant pneumonia and sepsis with buboes; incubation is shorter (1-6 days) and gram-negative bipolar-staining coccobacilli distinguish it on culture.
- Diagnosis
Culture or PCR establishes the diagnosis: confirmatory diagnosis is made by culture or polymerase chain reaction (PCR) of blood, tissue, or fluid samples; any case of inhalational anthrax should be…
- Management
First, start combination antimicrobial therapy immediately for suspected systemic (inhalational, gastrointestinal, or meningeal) anthrax: ciprofloxacin 400 mg IV every 8-12 hr or doxycycline 100 mg…
- Complications
Meningitis: occurs in up to 50% of systemic disease and carries a high mortality; hemorrhagic meningitis is a classic finding at autopsy in fatal cases.
- Prognosis
Inhalational anthrax has the highest mortality of the three clinical forms, particularly when treatment is delayed until systemic symptoms and radiographic mediastinal widening appear.
- Prevention
Anthrax vaccine absorbed (AVA) postexposure, three subcutaneous doses at 0, 2, and 4 weeks, started within 10 days of a known or suspected exposure, given together with 60 days of ciprofloxacin or…
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- Plague (Yersinia pestis infection)
Plague is infection with the gram-negative coccobacillus Yersinia pestis, transmitted by rodent fleas, presenting as bubonic, septicemic, or pneumonic disease with sudden fever and, in the bubonic form, an intensely painful regional bubo. Diagnosis rests on Gram/Wright-Giemsa stain and culture of aspirate, blood, or sputum, and treatment is empiric streptomycin or gentamicin, or a fluoroquinolone, started without waiting for confirmation because untreated pneumonic plague is uniformly fatal.
- Brucellosis
Brucellosis is a zoonotic infection from unpasteurized dairy, undercooked meat, or animal contact causing undulant fever, hepatosplenomegaly, arthralgia, and depression, diagnosed by extended-incubation blood or marrow culture and serum agglutination titer, and treated with doxycycline plus rifampin or gentamicin for six weeks.
- Melioidosis
Melioidosis is infection with Burkholderia pseudomallei, a CDC Class B bioterrorism agent endemic to Southeast and East Asia that presents in returning travelers as pneumonia or pyogenic hepatic abscess and is treated with IV ceftazidime or meropenem followed by oral trimethoprim-sulfamethoxazole.
- Q fever (Coxiella burnetii infection)
Q fever, caused by inhalation of Coxiella burnetii aerosols from infected livestock, most often produces a self-limited febrile illness with atypical pneumonia or hepatitis, but it is a major cause of culture-negative endocarditis when infection becomes chronic. Acute disease is treated with doxycycline for 2 weeks; endocarditis requires combination therapy for more than 18 months.
- Bacteremia
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