Acid-fast rods

Question 1

How is Mycobacterium tuberculosis transmitted?

Answer 1

human to human, via respiratory droplets

Question 2

T/F: M. Tuberculosis and M. avium-intracellulare can be resistant to multiple drugs.

Answer 2

true

Question 3

How is mycobacterium leprae transmitted?

Answer 3

prolonged exposure to actively shedding patients.

Question 4

What are the clinical manifestations of Mycobacterium tuberculosis? (2)

Answer 4

tuberculoloisis-initially asymptomatic or mild, can progress to hemoptysis. In most healthy hosts, cough resolves but can remain dormant for decades and reactivated by stress or immunosuppression. Non-pulmonary (miliary) TB- can infect any organ system. (rare)

Question 5

What is the morphology of Mycobacterium leprae?

Answer 5

acid fast rod

Question 6

Identify the major virulence/toxicity factors associated with Mycobacterium leprae. (2)

Answer 6

prefers colder temperatures in histiocytes, superficial endothelial cells and Schwann cells.

Question 7

What is the major reservoir for Mycobacterium avium-intracellulare? (2)

Answer 7

major reservoir is birds, but is ubiquitous in the environment.

Question 8

What lab findings are useful to help diagnose Mycobacterium leprae? (2)

Answer 8

cannot be grown on artificial medium; Acid-fast staining of skin lesion or nasal secretion.

Question 9

What lab findings are useful to help diagnose Mycobacterium tuberculosis? (5)

Answer 9

obligate aerobe; Very slow growth of snaki-like colonies is possible on egg-yolk agar; Ghon complex in lower lobes of CXR; DNA probes; Catalase and niacin tests Mantoux test.

Question 10

How does Mycobacterium leprae gram stain?

Answer 10

negative

Question 11

Identify the major virulence/toxicity factors associated with Mycobacterium tuberculosis. (3)

Answer 11

does not produce any toxin. Secretes a protein that prevents fusion of lysosome with phagosome inside macrophages. Very low infective dose (10 organisms)

Question 12

How does Mycobacterium tuberculosis gram stain?

Answer 12

negative

Question 13

How does Mycobacterium avlum-intracellulare gram stain?

Answer 13

negative

Question 14

What are the two forms of Hansen’s disease? Which form is worse?

Answer 14

Lepromatous and tuberculoid. Tuberculoid is self-limited, lepromatous is very severe (failed cell-mediated immunity).

Question 15

Identify relevant epidemiology and risk factors associated wit Mycobacterium tuberculosis. (3)

Answer 15

1/3 of the world’s population is infected. Native and African Americans; Immunocompromised.

Question 16

What lab findings are useful to help distinguish Mycobacterium avium-intracellulare from M. tuberculosis? (1)

Answer 16

blood or sputum culture will grow slightly faster than M. tuberculosis.

Question 17

What are common symptoms of TB? (4)

Answer 17

fever, night sweats, weight loss, hemoptysis

Question 18

What is the morphology of Mycobacterium avium-intracellulare?

Answer 18

acid fast rod

Question 19

F/F: All mycobacteria are acid-fast

Answer 19

true

Question 20

Why does M. tuberculosis prefer to colonize the lungs apices?

Answer 20

the apices have the highest partial pressure of oxygen.

Question 21

What are the clinical manifestations of Mycobacterium avium-intracellulare? (2)

Answer 21

tB-like pulmonary disease is highly resistant to antiTB drugs; presents almost exclusively in severely immunocompromised patients.

Question 22

What is the most common association with Mycobacterium tuberculosis?

Answer 22

causes more deaths (2-3 million each year) than any other bacteria.

Question 23

What is the morphology of Mycobacterium tuberculosis?

Answer 23

acid fast rod

Question 24

Identify relevant epidemiology and risk factors associated with Mycobacterium avium-intracellulare. (1)

Answer 24

AIDS or other immunosupression

Question 25

What is the major reservoir for Mycobacterium tuberculosis?

Answer 25

humans only

Question 26

T/F: M. leprae is an acid-fast bacterium that grows well in vitro.

Answer 26

False- M. leprae does not grow in vitro

Question 27

What are the major reservoirs for Mycobacterium leprae? (2)

Answer 27

humans and armadillos

Question 28

What are the clinical manifestations of Mycobacterium leprae? (2)

Answer 28

lepromatous leprosy-after years of incubation, symmetric skin nodules, peripheral neuropathy, loss of body hair; loss of sensation leads to secondary trauma, infection and disfigurement. Tuberculoid leprosy-in patients with partial immunity, hypopigmented lesions with reduced sensation. (milder disease)