Tuberculosis: 11.18.2022. IS + Study Questions Flashcards
Anatomy, physiology and ecology of the respiratory tract
Outline the pathogenesis of tuberculosis
- alveolar macrophages ingest mycobacteria.
bacteria is engulfed, but not destroyed. bacteria multiply within the host, and recruit more macrophages to the cite.
- bacteria survive and multiply in macrophages. additional macrophages/lymphocytes are recruited to the site. foamy macrophages develop.
lymphocytes collect around the infected macrophages, forming granulomas/tubercles. effector helper T cells release cytokines to activate the macrophages within the tubercle, but mycobacteria have induced their host to make lots of oil droplets, so they become foamy macrophages, which help them survive.
- fibrous capsule surrounds macrophages, excluding lymphocytes. tubercle forms.
- infected macrophages die, releasing mycobacteria and creating caseous necrosis (tissue death that has the texture of soft cheese)
- tubercle ruptures, releasing live mycobacteria into the airway.
Does infection with Mtb mean having tuberculosis the disease?
no. initial infection is typically asymptomatic. it’s a latent infection.
Differentiate between LTBI and ATBD
LTBI: latent tuberculosis infection. an asymptomatic Mycobacterium tuberculosis infection in which the bacterium is held in check by the immune system.
ATBD: active tuberculosis disease. chronic illness caused by Mycobacterium tuberculosis, characterized by slight fever, progressive weight loss, night sweating, persistent cough, often producing blood-streaked sputum.
How do we diagnose TB? (3)
TST (tuberculin skin test)
inject purified protein derivative from Mtb cultures. if infected, redness and a firm swelling (induration) @ injection site occurs after 48-72 hours.
IGRA (blood test). gives quicker and more specific results. good for people who have the BCG vaccine.
Xpert MTB/RIF assay. detects DNA of Mtb and closely related species.
Why is the BCG vaccine not used in the United States?
- not safe in immunocompromised test
- interferes with TST. it causes a positive TST, which eliminates an important way of diagnosing TB early in the disease when it’s easiest to treat.
Which populations are most susceptible to tuberculosis?
immunocompromised. people living in poverty, people with AIDS, prisoners, and immigrants.
What is the concern with the current tuberculosis treatments?
concern: Mtb can evolve when people don’t take their combination therapy drugs. start to feel better and stop taking their medication.
solution: DOT (directly observed therapy). healthcare workers watch patients swallow their pills.
How are the symptoms of tuberculosis different from pneumonia?
longer duration and more systemic: weight loss, night sweats
What are some characteristics of Mtb? (5) which of these make Mtb so hardy?
- bacillus shape
- acid-fast
- aerobe
- grows slowly
- mycolic acid in cell wall
Why does treatment for Mtb have to be for many months?
bacteria is hardy and has a long generation time.
to clear the infection because of the long generation time of Mtb and its resistance to destruction
How does Mtb evade the immune system?
manipulate and multiply inside phagocytic cells
what is the causative agent of tuberculosis?
Mycobacterium tuberculosis
what is a granuloma? what’s a granuloma called in TB?
localized collection of immune cells.
tubercles.
what is a tubercle?
the granulomas of tuberculosis
