Anthrax and Plague

Question 1

Gram (+) bacteria

Spore forming

Aerobic

Non-motile

Answer 1

Bacillus anthracis (Anthrax)

Motile = B. cereus (food poisoning)

Question 2

Is anthrax contagious?

Answer 2

NO

(i.e., it will never become a spore again)

Question 3

How does anthrax survive so well?

Answer 3

Infectious spores are heat resistant (survives in soil and gets transmitted by animals)

Question 4

What are the only 2 virulent species of the bacillus family?

Answer 4

B. anthracis and B. cereus

Most other species are opportunistic pathogens of low virulence potential

Question 5

Pathobiology of anthrax

Answer 5

Spores from goat, cow, or herbivore products enter human via: cutaneous abrasion, ingestion, or inhalation

Question 6

Cutaneous anthrax

Answer 6

Most common

Spores germinate and multiply locally, anthrax toxin secreted locally, causes tissue hemorrhage and necrosis (malignant pustules)

Key words: black eschar, painless edema

Question 7

GI anthrax

Answer 7

Ingestion of spore-contaminated meat

Rare, but > 50% lethal

Spores germinate and multiply locally in oropharynx or intestines, lesions in throat/intestines leads to dysentery

Question 8

Inhalation anthrax

Answer 8

Must be < 5 microns

Woolsorters and bioterrorism (100% mortality)

Incubation period: 1-43 days

Spores germinate and multiply in respiratory tract, bacteria enter bloodstream and divide, anthrax toxin secreted systemically

Nonspecific symptoms for 3-5 days; terminal phase defined by hemorrhagic mediastinitis

Question 9

How to test for inhalational anthrax

Answer 9

CXR is pathognomonic:

widened mediastinum w/ pleural effusions

NO infiltrates

Question 10

Virulent factors of anthrax

Answer 10

PA (protectice antigen): binds cell membrane and mediates endocytic entry of EF and LF

EF (edema factor): adenylate cyclase activity = increased cAMP = edema and inhibiton of PMNs

LF (lethal factor): cell death via MAPK signal disruption

Question 11

Tx for anthrax

Answer 11

Combination Abx Therapy:

cipro/doxy + clinda + rifampin

Question 12

Vaccine for anthrax

Answer 12

inactivated

composed primarily of PA (i.e., anti-PA vaccine)

Question 13

Only medically important bacteria with protein rather than polysaccharide capsule

Answer 13

Bacillus anthracis

Look for: spores forming rods which line up in long filaments

Question 14

Gram (-) bacteria

Grows on MacConkey’s agar

Lactose non-fermenter

Bipolar staining

Answer 14

Yersinia pestis

Question 15

Pathobiology of Yersinia pestis

Answer 15

Transmitted from rodents to humans by flea vector (exception being pneumonic plague which is person to person)

Phagocytosed (killed in PMNs, released by monocytes), transported to regional lymph nodes, multiplies and stimulates inflammation, regional lymphadenitis (buboes) often in groin within macrophages, intracellular replication and spread, invades liver, spleen, skin, and lungs, endotoxin causes DIC, cutaneous hemorrhagic necrosis causes black color

Question 16

How is Yersinia pestis resistant to phagocytosis

Answer 16

Capsular F-1 antigen prevents it

Question 17

Why did the researcher who was working with Yersinia pestis die?

Answer 17

His unknown iron storage disease made it easier to contract

Question 18

Vaccine for Yersinia pestis

Answer 18

Killed and attenuated vaccines are available

antibodies against F1 antigen

Question 19

How did Pneumonic Plague emerge from the Bubonic Plague?

Answer 19

With septicemia, Y. pestis can seed alveoli and cause pneumonia (septic pulmonary emboli)

This allows aersol transmission from person to person

Question 20

Bipolar staining resembling safety pin

Answer 20

Yersinia pestis

Question 21

Vector for Yersinia pestis

Answer 21

Flea

(bites prairie dog, coagulase made by Yersinia pestis causes the gut of the flea to coagulate, flea regurigitates “gut content” into the next victim it bites)

Note: don’t jump straight to Y. pestis if the vignette mentions a prairie dog (must also consider monkeypox)