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Bacillus anthracis

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Bacillus anthracis

a. Structure
i. Encapsulated
ii. Gram Positive Rod
b. Pathobiology:
i. Spore forming
ii. Facultative anaerobe
iii. Virulence factors
1. Protective antigen
2. Edema factor (EF) –  adenylate cyclase activity  ↑[cAMP]  edema and inhibition of polymorphonuclear leukocytes
a. Likely responsible for characteristic edematous borders of black eschar in cutaneous anthrax
3. Lethal Factor (LF) – protease  Cell Death
4. Toxins (Combination of above factors):
a. Edema Toxin – PA + EF
b. Lethal Toxin – PA + LF
5. Capsule – contains poly-D-glutamic acid (i.e. protein)
c. Epidemiology
i. Reservoir – herbivores
ii. Spores were delivered in mail in 2001 (i.e. “2001 Anthrax Attacks”)
iii. Spread to humans via inoculation, ingestion, inhalation
d. Laboratory diagnosis
i. Microscopy
1. Spores – view with spore strain, incubated with low CO2
2. Non-hemolytic
3. Non-motile
ii. PCR
e. Disease - Anthrax
i. Manifestations
1. Cutaneous anthrax
a. Painless papule, develop to ulcer and necrotic, black eschar
b. Lymphadenopathy, edema
2. Gastrointestinal anthrax
a. Ulcers in mouth/esophagus
b. Nausea, vomiting, malaise
3. Inhalation anthrax
a. Prolonged latent period (spores)
b. First stage: Fever, myalgias, non-productive cough, malaise
c. Second stage: Fever, edema, enlargement of mediastinal lymph nodes
d. Meningeal symptoms
ii. Therapy
1. Current treatment: ciprofloxacin or doxycycline, combined with 1 or 2 additional antibiotics
2. Penicillin resistance is observed
a. If not resistant, use of Penicillin G (parenterally) is sufficient
iii. Prevention and control
1. Vaccination available, although less effective
2. Recommendation -  vaccination of animal herds

Related concepts
1. Gram-positive bacteria
2. Gram-positive bacilli
3. Bacillus
4. B. anthracis
5. Anthrax
6. Lethal toxin
7. Lethal factor
8. Edema factor
9. Edema toxin

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