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Types of Clinical Anthrax
Inhalational anthrax (Lethal Dose [10-50 spores]
LD50 believed to be 10,000-20,000 spores in the human
with intact immune system) follows deposition of spore-bearing
particles into the alveolar spaces. Macrophages ingest the spores,
some of which undergo lysis and destruction. Surviving spores
are transported by macrophages to mediastinal lymph nodes, germinate
into vegetative cells en route and intensively multiply once
in the lymph nodes. Once multiplication has begun, disease follows
rapidly. The infection rapidly progresses through the following
pathogenetic stages:
- Accumulation of vegetative cells in the lymphatic system and
lymphoid tissue-containing organs (spleen, liver, and lymph nodes).
This stage is characterized by low bacteremia and low toxemia
- Increasing bacteremia, toxemia, and rapidly accumulating organisms
of bacilli in the lymphatic system and organs
- Rapidly accumulating organisms of anthrax toxins in blood and lymph
- Increasing massive mediastinal edema, hemorrhagic thoracic
lymphadenitis, hemorrhagic mediastinitis, and sometimes hemorrhagic
meningitis
- Increasing respiratory dysfunction and increased vascular permeability
induced by anthrax toxins
- Mediastinitis
- Sepsis
- Septic shock and death
Cutaneous anthrax (LD50 is about 10-50 spores) occurs following the
deposition of anthrax spores into the skin through cuts or abrasions.
After the spores germinate in skin tissues, toxin production results in
local edema. This route of infection has the following stages of development:
- Initial pruritic macule or papule
- Spherical ulcer, sometimes with 1- to 3-mm vesicles around periphery
- Black, painless, depressed eschar, usually associated with extensive
local edema
- Lymphadenitis and painful lymphadenopathy can occur with associated
systemic symptoms
Gastrointestinal (GI) anthrax (LD50 several hundreds of thousands of spores)
occurs as a result of germination of anthrax spores deposited in the upper
or lower gastrointestinal tract. Depending on the focus of infection, this
can result in either the oro-pharyngeal (upper GI tract) or ileocecal form
(lower GI tract). In the oro-pharyngeal form, an oral or esophageal ulcer
leads to the development of regional lymphadenopathy, edema, and sepsis.
The ileocecal form leads to partial necrosis of the intestinal tract,
resulting in bloody diarrhea, acute abdomen, ascites, or sepsis.
Diagnosis and Treatment
Presenting Syndromes
- Influenza
- Pulmonary
- Meningitis
- Stridor
- Pleural effusions
- Mediastinitis
- Respiratory Distress
- Septic Shock
- Cyanosis
- Elevated White Blood Cells (WBC)
- Edema
Diagnostic Samples : Blood, Cerebral Spinal Fluid (CSF)
Differential Diagnosis : Tularemia, Plague, Diphtheria
Isolation/Decon Precautions : Standard precautions
Therapy for Inhalational Anthrax:
From CDC guidelines published in
the
MMWR, 10/26/2001; 50(42), 909-919
For mass-casualty settings, ciprofloxacin or doxycycline may be used.
Ciprofloxacin 400 mg Intravenous (IV) q 12h (Peds: 10-15mg/kg q 12h dosing up to 1 Gm/day)
OR
Doxycycline 100 mg IV q 12h (Peds: >8 yrs and > 45 kg, 100 mg IV q 12h; >8 yrs and <45 kg, 2.2mg/kg IV q 12h; <8yrs, 2.2mg/kg IV q 12h)
Plus
One or two additional antimicrobials : Rifampin, Vancomycin,
Penicillin, Ampicillin, Chloramphenicol, Imipenem, Clindamycin,
or Clarithromycin
Begin IV treatment initially. Change to oral antibiotic therapy when
clinically appropriate: Ciprofloxacin 500 mg orally (po) twice a day (BID) OR Doxycycline 100 mg po
BID. (Peds: Ciprofloxacin 10-15 mg/kg po q 12, OR Doxycycline as follows: >8 yrs
and >45 kg, 100 mg po BID; >8 yrs and <45 kg, 2.2mg/kg po BID; <8yrs, 2.2mg/kg
po BID). Therapy should continue for 60 days IV and po combined.
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