Micro - Anthrax Flashcards
B. anthracis = (G+, G-) (aerobe, anaerobe) (spore forming or not) (shape)
G+ facultative anaerobe, spore forming, rod
Primary reservoir of naturally-occuring anthrax
Cows/soil
Why don’t farmers contract natural anthrax?
Spores clump together and stick to soil
How does B. anthrax look on blood smear/CSF?
BoX cars
How long can anthrax spores remain viable in soil?
100 years
Problem with anthrax infections?
Misdiagnosed
Category A bioterrorism agents
Tularemia, anthrax, plague
Category B bioterrorism agent
Brucella
Two major virulence factors of anthrax
- Antiphagocytic, non-antigenic capsule
2. Exotoxin
Anthrax capsule made up of:
Poly-d-glutamic acid
3 subunits of anthrax toxin and their function
B = protective antigen; binds to host cell receptors and facilitates endocytosis then entry into cytoplasm once inside cell A1 = edema factor; AC that increases cAMP which causes swelling, mediastinal edema A2 = lethal factor; MMP that inhibits MAPKs to disrupt cell signaling and innate immunity
What causes swelling in cutaneous anthrax infection?
Edema factor (A subunit) of toxin (ON TEST!!!)
Two possible anthrax disease
Cutaneous or inhalational
Characteristic lesion of cutaneous anthrax
Swollen eschar (necrotic, black skin lesion)
Two phases of inhalational anthrax
- Flu-like sx + SOB + N/V + CP
2. Hemorrhagic mediastinitis + pleural effusion
Which is more fatal if untreated: cutaneous or inhalational anthrax?
Inhalational (universally fatal; cutaneous only 20% fatal)
Sx of GI anthrax
Pharyngitis, lymphadenopathy, severe bloody diarrhea, vomiting
(no reported cases in US)
Worst case systemic anthrax
Hemorrhagic meningitis
Key signs of inhalational anthrax
- Hilar lymph node infection
2. Mediastinal widening
Mechanism of disease
- Spores inhaled
- Spores taken up by alveolar/skin/GI macropahges
- Spores germinate and become encapsulated
- Vegetative cells form and release toxin
- Spores disseminate
- Toxin causes swelling, sepsis, necrosis
Incubation period for anthrax
6 weeks (germination of pores in macrophages)
What to do if someone is exposed to anthrax?
Give prophylactic cipro for 40 days (incubation period is 6 months)
3 key tests for dx anthrax
- Gram stain (G+)
- Immunofluorscent Ab stain of CSF
- Blood smears for boxcar chains
Flu vs. inhalational anthrax
Flu won’t have SOB, N/V
Anthrax won’t have rhinorrhea
What can also cause mediastinal widening?
- Histo (no pleural effusion)
- Cardiac collapse
- Silicosis, sarcoidosis (chronic not acute)
What can also cause skin lesions?
Staph and strep (purulent not necrotic lesions)
What things point to anthrax after an act of bioterrorism?
Cluster of people with severe flu-like sx; skin/pneumonic lesions in mail handlers; eschars; WIDENED MEDIASTINUM ON XRAY
Tx inhalational anthrax
Cipro or doxy + another Abx (ampicillin)
Must be immediate
MAB for anthrax tx
Against B subunit of toxin/protective antigen
Used against Abx-resistant strains
How to get rid of anthrax spores?
Boil for 10 min
