Acid-fast rods Flashcards
How is Mycobacterium tuberculosis transmitted?
human to human, via respiratory droplets
T/F: M. Tuberculosis and M. avium-intracellulare can be resistant to multiple drugs.
true
How is mycobacterium leprae transmitted?
prolonged exposure to actively shedding patients.
What are the clinical manifestations of Mycobacterium tuberculosis? (2)
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)
What is the morphology of Mycobacterium leprae?
acid fast rod
Identify the major virulence/toxicity factors associated with Mycobacterium leprae. (2)
prefers colder temperatures in histiocytes, superficial endothelial cells and Schwann cells.
What is the major reservoir for Mycobacterium avium-intracellulare? (2)
major reservoir is birds, but is ubiquitous in the environment.
What lab findings are useful to help diagnose Mycobacterium leprae? (2)
cannot be grown on artificial medium; Acid-fast staining of skin lesion or nasal secretion.
What lab findings are useful to help diagnose Mycobacterium tuberculosis? (5)
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.
How does Mycobacterium leprae gram stain?
negative
Identify the major virulence/toxicity factors associated with Mycobacterium tuberculosis. (3)
does not produce any toxin. Secretes a protein that prevents fusion of lysosome with phagosome inside macrophages. Very low infective dose (10 organisms)
How does Mycobacterium tuberculosis gram stain?
negative
How does Mycobacterium avlum-intracellulare gram stain?
negative
What are the two forms of Hansen’s disease? Which form is worse?
Lepromatous and tuberculoid. Tuberculoid is self-limited, lepromatous is very severe (failed cell-mediated immunity).
Identify relevant epidemiology and risk factors associated wit Mycobacterium tuberculosis. (3)
1/3 of the world’s population is infected. Native and African Americans; Immunocompromised.
What lab findings are useful to help distinguish Mycobacterium avium-intracellulare from M. tuberculosis? (1)
blood or sputum culture will grow slightly faster than M. tuberculosis.
What are common symptoms of TB? (4)
fever, night sweats, weight loss, hemoptysis
What is the morphology of Mycobacterium avium-intracellulare?
acid fast rod
F/F: All mycobacteria are acid-fast
true
Why does M. tuberculosis prefer to colonize the lungs apices?
the apices have the highest partial pressure of oxygen.
What are the clinical manifestations of Mycobacterium avium-intracellulare? (2)
tB-like pulmonary disease is highly resistant to antiTB drugs; presents almost exclusively in severely immunocompromised patients.
What is the most common association with Mycobacterium tuberculosis?
causes more deaths (2-3 million each year) than any other bacteria.
What is the morphology of Mycobacterium tuberculosis?
acid fast rod
Identify relevant epidemiology and risk factors associated with Mycobacterium avium-intracellulare. (1)
AIDS or other immunosupression
What is the major reservoir for Mycobacterium tuberculosis?
humans only
T/F: M. leprae is an acid-fast bacterium that grows well in vitro.
False- M. leprae does not grow in vitro
What are the major reservoirs for Mycobacterium leprae? (2)
humans and armadillos
What are the clinical manifestations of Mycobacterium leprae? (2)
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)
