Anthrax and the Plague Flashcards
What do you know about Bacillus?
Gram positive, aerobic, spore-forming rod
Seen as long filaments on microscopy (box cars)
B. Anthracis and B. Cereus are two virulent forms
Herbivores are infected while grazing and spread to humans cutaneously, ingestionally, or inhalationally.
What are the 3 virulence factors of Bacillus?
Poly-d glutamic acid capsule allowing it to avoid phagocytosis
Two Toxins: Edema Toxin and Lethan Toxin
What are the components of Edema Toxin?
Edema Factor a calmodulin dependents adenylate cyclase that converts ATP to cAMP and causes edema.
Protective Antigen which allows binding and forms pores in the endocytosed vesicles
What are the components of Lethal toxin?
Lethal Factor: a zinc metalloproteinase that cleaves MAPKK inhibiting signal tranduction pathways in macrophages
Protective Antigen: allows binding and forms pores in the endocytosed vesicles
What are the three forms of clinical Anthrax?
Cutaneous, GI, Inhalational
What are the clinical features of cutaneous anthrax?
95% of all cases
Associated with occupational exposure to animals
Papules form and progress to central necrosis with a painless black eschar that will completely resolve in 80-90% of cases
What are the clinical features of gastrointestinal anthrax?
Rare
Follows the ingestion of spore contaminated meat
Forms ulcers at the site of invasion leading to regional lymphadenopathy, edema, and sepsis.
Mortality is greater than 50%
What are the clinical features of inhalational anthrax?
Incubation period of 1-43 days
Varied presentation:
1) Dyspnea, stridor, cyanosis, chest pain, edema, shock and death
2) hemorrhagic mediastinitis, hemorrhagic pleural effusions seen on CXR
Meningitis present in 50% of cases, GI Hemorrhage present in up to 90%
What is the treatment for Anthrax?
Ciprofloxacin or Doxycycline for 60 days to prevent spores that germinate later than the initial infection
What is the composition of the currently licensed vaccine against anthrax?
Inactivated vaccine derived from primarily Protective antigen of an attenuated, non-encapsulated strain. Given IM at 0,4,6,12 and 18 weeks with yearly boosters
What are the bacteriologic features of Yersinia Pestis?
Gram negative rod with a “safety pin” appearance that grows well on MacConkey’s again.
Flea vector is required for transmission
Occurs in AZ, CO, NM and UT
How is Yersinia Pestis diagnosed?
MacConkey’s agar or sheeps blood again for 5 to 7 days
What is the transmission cycle for Yersinia Pestis?
Fleas bites and regurgitates bacteria causing a vesicular lesion at the bite site. Organisms are phagocytosed and killed by PMNs but released from monocytes. Once released resists phagocytosis, spreads to the lymphatic, localizes in lymph nodes causing a bubo. Then either stops or disseminates leading to bacteriemia
