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Pulm > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

Characteristics of Mycobacterium tuberculosis

A
  1. Acid fast bacillus
    - mycolic acid within the cell wall retains the carbolfushcin stain
  2. Obligate aerobe
  3. Slow growth rate (cultures held for 6-8 weeks before finalized)
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2
Q

Secondary infection of TB usually occurs where?

A

Apices of the lungs

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3
Q

What are the structures and properties that contribute to the pathogenesis of TB?

A
  1. Cell Wall: Many waxy-like substances that make the cell wall impermeable to many host defense systems
  2. Cord factor - Inhibits macrophage maturation and induces TNF-alpha release
  3. Sulfatides - inhibits phagolysosomal fusion
    * allows MTB to grow inside the macrophage (protected from host immune system)
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4
Q

What protein may play a role in the inhibition of phagolysosomal fusion with a macrophage?

A

PknG

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5
Q

What is the most important determinant of whether overt TB disease will occur?

A

The adequacy of the host’s cell-mediated immune response

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6
Q

What cell types mount the response that leads to containment of the infections

A
  1. Th1 - response leads to granuloma formation and caseous necrosis
  2. Macrophages - once activated the secrete TNF and cytokines to recruit more monocytes
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7
Q

Risk Factors for TB

A
  1. Prison (crowded conditions)
  2. Immigrant from high burden country (Mexico)
  3. Malnourished
  4. Alcoholism
  5. Poverty
  6. AIDs
  7. Debilitating illness
  8. Elderly
  9. Certain diseases
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8
Q

Which disease increase the rick for TB

A
  1. DM
  2. Hodgkin lymphoma
  3. CKD
  4. Immunosuppression
    5 RA (on TNF-alpha antagonists)
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9
Q

What percent of people infected with MTB actually develop the disease?

A

10%

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10
Q

Clinical manifestations of seconday/reactivated TB

A
  • Insidious onset*
    1. malaise
    2. anorexia and wt loss
    3. low-grade fever
    4. SOB
    5. night sweats
    6. Cough productive of blood-streaked and/or purulent sputum
    7. Pleuritic pain (Some ppl)
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11
Q

Clinical manifestations of progressive primary TB?

A

Presents like an acute bacterial pneumonia

  • CXR with infiltrates or lobar consolidation
  • hilar LAD
  • pleural effusion
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12
Q

Clinical manifestations of Miliary/disseminated TB?

A
  1. Lymphoheme. disseminations usually follow primary TB infection
  2. CXR - looks like there a bunch of seeds all over it
    - dyspnea and cough
  3. Liver: RUQ pain w/ N/V
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13
Q

PTs with Miliary/disseminated TB are susceptible to what diseases?

A
  1. Meningitis
  2. Pott’s disease (vertebral osteomyelitits)
  3. GI (N/V and diarrhea)
  4. Urinary (Sterile pyuria, hematuria, proteinuria)
  5. Adrenal insufficiency, epididymitis, prostatiis
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14
Q

Dx of TB

A
  1. Acid Fast stain on sputum with a culture being done at same time
  2. If initial Acid fast is positive, PCR for rapid results
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15
Q

How to culture MTB?

A

Lowenstein-Jensen agar
- takes 3-6 weeks to grow

Liquid media shows results in as early as 2 weeks

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16
Q

Tx of secondary/primary pulmonary TB

A

If suspicious, begin tx:

  • Initial 4 drug tx (RIPE)
    1. Isoniazid
    2. Rifampin
    3. Pyrazinimide
    4. Ethambutol
  • once susceptibility known and if susceptible. Stop ethambutol
  • After 2 months of RIPE/RIP, can stop PZA, and contine with RI for 4-7 months to complete 6-9 month therapy
17
Q

Tx of Miliary TB

A

Tx with RIPE for 9-12 months

  1. Isoniazid
  2. Rifampin
  3. Pyrazinimide
  4. Ethambutol
18
Q

Why is a long course of therapy required for TB?

A
  1. Organism grows slowly
  2. There are metabolically inactive organisms within the lesion
  3. Organism is located intracellularly
  4. Caseous material blocks penetration by drugs
19
Q

Multidrug resistant (MDR) TB is most commonly resistant to which drugs?

A
  1. Isoniazid

2. Rifampin

20
Q

Describe the resistance in Extended drug resistant (XDR) TB

A

resistant to:

  1. Isoniazid
  2. Rifampin
  3. Flouroqinolone
  4. at least one addition drug
21
Q

What is a risk factor for the development of TB resistance to Tx? How is it prevented?

A

Noncompliance

- Directly observed therapy (DOT)

22
Q

All stages of HIV are associated with increased rick of TB, even with HAART. Why?

A

no immune response and so no bronchial damage and few acid fast bacilli in sputum

23
Q

Dx of Latent TB

A

PPD: Purified protein derivative

  • intradermal injection of tuberculin material which stimulates a delayed type hypersensitivity rxn
  • causes induration within 48-72 hours in positive
  • not perfect due to vaccines used in other countries and also due to nontuberculous mycobacterial infections

IGRA: interferon gamma release assay

  • PT blood cells exposed to antigens from MTB and amount of IF-gamma released from cells is measure.
  • NO false positive with BCG vac. or other organisms
24
Q

Tx for latent TB

A
  1. Isoniazid for 9 months
    - or-
  2. Isoniazid and Rifapentine for 3 months
25
Q

What is a Positive PPD

A
  • Measure induration (Bump on arm)
  • Positive if:
    1. induration >15mm and no known risk factors
    2. Indur. 10-15mm - homeless, IVDU, nursing home, recent immigrant, or child

Pulm (14 decks)

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