Microbiology-Anthrax and Plague

Question 1

When is anthrax contagious?

Answer 1

Never, the spores are the only contagious form and we don’t produce spores.

Question 2

Watery diarrhea from Chinese rice sitting out all day

Answer 2

Bacillus cereus spores

Question 3

Spore-forming gram-positive rods

Answer 3

Bacillus (aerobes) and clostridia (anaerobes). They sporulate from a vegetative rod to a spore and then germinate into a rod (bacillus anthracis chains shown below).

Question 4

Virulence factors of bacillus anthracis

Answer 4

Poly D-glutamic acid capsule (evades phagocytosis), replicates in blood stream, produces EDEMA TOXIN = edema factor (EF=A subunit) + protective antigen (PA=B subunit), produces LETHAL TOXIN = lethal factor (LF=A subunit) + protective antigen (PA=B subunit).

Question 5

Antibody to what region of bacillus anthracis neutralizes the toxin?

Answer 5

Anti-PA antibody. This prevents PA from binding to macrophages and forming a pore so the A subunits can enter.

Question 6

Function of B. anthracis edema factor?

Answer 6

Calmodulin-dependent bacterial adenylate cyclase. Causes fluid accumulation at site of infection. (like pertussis).

Question 7

Function of B. anthracis lethal factor?

Answer 7

Zinc-metaloprotease that cleaves MAPKK -> disrupts MAPK signal transduction in macrophages -> inactivates macrophages and minimizes immune response.

Question 8

B. anthracis reservoir

Answer 8

Soil, especially in grazing goats, cattle and sheep hides. Can also get from contaminated meat and IV drug abuse (heroin wrapped in goat skin).

Question 9

3 manifestations of anthrax

Answer 9

CUTANEOUS (papules -> central necrosis -> black eschar, painless, edematous, resolves 90% of time). GASTROINTESTINAL: ingestion of spore-contaminated meat, ulcers at site of invasion, regional lymphadenopathy, edema, hemorrhage, sepsis, 50% mortality. INHALATIONAL (

Question 10

Prophylaxis for inhalational anthrax

Answer 10

Ciprofloxacin/doxycycline + clindamycin + rifampin for 60 days!

Question 11

Licensed anthrax vaccine

Answer 11

Non-encapsulated, attenuated live vaccine

Question 12

Lab characteristics of the bacteria that causes plague.

Answer 12

Yersinia pestis: gram-negative rod that grows on MacConkey’s agar and stains with Wayson’s stain (looks like safety pins).

Question 13

Only type of plague that transfers person to person

Answer 13

Pneumonic plague (middle ages), all other plagues need fleas to transfer the bacteria from the reservoir (rats, squirrels, prairie dogs, mice, cats, rabbits) to humans.

Question 14

Pathogenesis of plague

Answer 14

Flea regurgitates bacteria on bite -> Phagocytosis -> Released from monocytes -> Lymphatics -> Bubo -> Resolution or Dissemination -> Bacteremia w/pneumonia, meningitis and/or septic shock.