Pulmonary Anthrax

Author: Samantha Selesny, PGY3
Associate Editor of Emergency Medicine Toxicology, EMRounds

Background

Anthrax: Acute bacterial infection caused by aerobic, gram positive rod, Bacillus anthracis

Capable of surviving inhospitable conditions through formation of endospores
Incubation period is 10 days with no ability for human to human transmission – therefore no need for respiratory isolation
BUT potential harbors of spores (i.e. patient clothes) need to be isolated and decontaminated with 10% bleach

3 Types: Inhalational, Cutaneous (95%), and Gastrointestinal

1. Inhalational: “woolsorter’s disease”

Usually results from handling unsterilized, imported animal hides or raw wool.
Biphasic course:
1. Prodromal period: flu-like illness-fever/dry cough/myalgias x 2-3 days
  - Antibiotic therapy can be successful if initiated during the prodromal phase of the disease
2. Acute phase/Rapidly fulminant bacteremic phase: severe respiratory distress: hypoxia, cyanosis, shock, mediastinitis
  - Almost always fatal if fulminant phase is reached

Pathophysiology of Pulmonic Anthrax:

B. anthracis spores are phagocytosed by alveolar macrophages and transported to mediastinal lymph nodes.
There they germinate, multiply, and release toxins, causing hemorrhagic necrosis of the thoracic lymph nodes draining the lungs,
This leads to hemorrhagic mediastinitis and, can also lead to necrotizing pneumonia
The organisms then become bloodborne, causing bacteremia and, in some cases, meningitis.

2. Cutaneous anthrax (95%)

Begins with pruritic cutaneous macule at inoculation site (usually fingers) >> ulcerative lesion with multiple infectious serosanguinous vesicles containing anthrax bacillus
Progresses to painless black eschar and fall off within 2 weeks (See Figure 1 below)
Most skin lesions heal spontaneously, but 10-20% of untreated patients progress to septicemia and death. When treated, rarely results in fatalities

3. GI Anthrax:

Ingestion of insufficiently cooked meat from infected animals.
Patients present with fever, nausea, vomiting, abdominal pain and mucosal ulcers which can cause GI hemorrhage, sepsis, and perforation.
Mortality is about 50% even with antibiotic treatment

CXR (Figure 2)
- Widened mediastinum- hemorrhagic mediastinitis
- Infiltrate, pleural effusion
- Reflective of hemorrhagic effusions
- Hyperdense mediastinal lymphadenopathy
When diagnosis suspected, CT Chest is test of choice

Airway management
Contact CDC
Post-exposure Prophylaxis:
- Vaccinate at day #0, #14, #28
- Ciprofloxacin 500 mg PO q12 hrs daily x60 days OR
- Doxycycline 100 mg PO q12 hrs x 60 days
Inhalational Anthrax is highly susceptible to PCN, amoxicillin, doxy, erythromycin, ciprofloxacin
Resistant to 3rd generation cephalosporins
- FIRST LINE: Ciprofloxacin 400 mg IV q12 hrs x60 days
- Doxycycline IV (only if allergic to ciprofloxacin) PLUS Clindamycin
Consults: Critical Care and Infectious disease
Dispo: Admission to ICU – can progress to septic/hemorrhagic shock

Meningitis

Associated all types of anthrax but mostly pulmonic
50% of patients with inhalational anthrax will develop hemorrhagic meningitis.
CSF: elevated protein, low glucose, and a positive Gram stain, and culture (See Figure 3 below)
Parenchymal brain hemorrhage may be so severe that a grossly bloody lumbar puncture may be confused with a traumatic tap.
Delirium or coma follows quickly, and refractory seizures, cranial nerve palsies, and myoclonus have been reported

References:

“Zoonotic Infections.” Tintinalli’s Emergency Medicine Manual, 8e Tintinalli JE, Ma O, Yealy DM, Meckler GD, Stapczynski J, Cline DM, Thomas SH
“Biological Warfare Agents.” Goldfranks Toxicologic Emergencies, 9th ed., McGraw-Hill, 2002.
https://wikem.org/wiki/Anthrax
https://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-anthrax?search=anthrax%20inhalation&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1