Anthrax / Plague (lecture) Flashcards
Sheep herder presents with non-specific respiratory illness and reports that a lot of his sheep have died recently and displayed hemorrhage. What is expected on staining of the most likely causal organism and its virulence factor?
This is likely Anthrax caused by Bacillus anthracis. Staining will show long G + rods (often called boxcars).
B toxin is the most virulent toxin produced. It has edema factor (EF) and lethal factor (LF) components.
EF acts via calmodulin to increase adenylate cyclase –> incr. cAMP –> incr. edema.
LF acts via the MAPKK pathway, resulting in down regulating MAPK –> cell death (http://www.pnas.org/content/97/6/2405.figures-onl)
What are the two bacterial genre mentioned in class that are spore formers and the main distinction between them?
Clostridia are strict anaerobes (cat -, superoxide dismutase -)
Bacillus are facultative anaerobes or aerobes
What is unique about Bacillus capsules?
They are made of D-glutamic acid (an amino acid), whereas most capsules are made of polysaccharides
What are the various forms of anthrax and their relative moralities?
Cutaneous: 80-90% complete resolution
GI: 50% mortality
Inhalation: 90% mortality with delayed Tx
What type of vaccine is given for prevention of anthrax?
Killed attenuated
How can one distinguish an anthrax eschar from a spider bite?
The anthrax eschar is painless.
What is the chest x-ray finding in inhalation anthrax?
Widened mediastinum with pleural effusions without infiltrates http://wwwnc.cdc.gov/eid/article/7/6/01-0604-f1
For ref. here is an aortic dissection x-ray: https://dailyem.wordpress.com/2012/10/01/aortic-dissection-review/
- Notice the anthrax associated widening starts much more cephalad
What is the typical time course of Abx treatment in anthrax treatment?
60 days of Cipro or Doxy + Clindamycin + Rifampin
What is the main component of the anthrax vaccine?
Protective antigen
Patient presents with a painful eschar on his trunk and necrotic fingers. He has a recent history of travel to the Southwest US for a camping trip. The causal organism shows G negative coccobacilli with a central clearing. It also grows well on MacConkey agar, with a yellow color resulting. What is the likely agent and the likely mode of contraction?
This describes Yersinia pestis. Yellow Mac = non lactose fermentor.
Its life cycle includes rodents and fleas. Most likely the patient was bitten by a flea on his camping trip.
Note: Y. pestis is most prevalent in the SW and Western portions of the US
Once infected, what is the required step for Yersinia pestis to become virulent?
It must be released from monocytes, at which point it becomes encapsulated.
