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Patho Midterm 2 > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

Tuberculosis?

A

An infectious disease caused by Mycobacterium tuberculosis

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2
Q

Explain the bacterium.

A
  • It is a rod-shaped, aerobic bacterium
  • resistant to destruction and persist in necrotic and calcified lesions for prolonged periods and remain capable of reinstating growth
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3
Q

Mode of transmission?

A

Airborne infection spread by droplet nuclei (coughing; sneezing; talking)

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4
Q

What increases the risk of developing TB?

A

Overcrowded living conditions

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5
Q

Why is cell-mediated response important?

A

It is important in walling off the tubercle bacilli and preventing the development of active TB

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6
Q

What happens if your cell immunity is impaired?

A

You are more likely to develop active TB

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7
Q

What does a positive TB test indicate?

A

You are infected but it doesn’t mean you have active TB

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8
Q

How many cases of TB occur in Canada each year and how many deaths?

A

1600; 130deaths

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9
Q

In Canada, who is it more common in?

A

Foreign borne persons and Canadian-borne persons in northern Canada

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10
Q

List the microbes that are responsible.

A

Mycobacterium, M. Tuberculosis

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11
Q

Explain the structure.

A
  • slender, rod-shaped aerobic bacterium that do not form spores.
  • Have outer waxy capsule
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12
Q

What does the outer waxy capsule do for the bacterium?

A

It makes them more resistant to destruction

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13
Q

Why is infection most frequently in the lungs?

A

The tubercle bacilli are strict aerobes that thrive in an oxygen rich environment. The lungs have the greatest concentration of O2 and ventilation.

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14
Q

What is the patho of TB centered on?

A

The development of a cell-mediated IR that gives resistance to the organism and development of tissue hypersensitivity to the tubercular antigens.

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15
Q

What do the destructive features on the disease result from?

A

Hypersensitivity IR rather than the destructive capabilities of the tubercle bacillus

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16
Q

What are the primary cells that are infected by M. TB?

A

Macrophages

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17
Q

Where does the inhaled droplet nuclei deposit? Briefly explain

A

Inhaled droplet nuclei pass down the bronchial tree without settling on the epithelium and are deposited on the alveoli

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18
Q

What happens once the inhaled droplet nuclei is deposited on the alveoli?

A

Bacilli are phagocytised by alveolar macrophages but resist killing because cell wall lipids of M. TB blocks fusion of phagosomes and lysosomes

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19
Q

Whys is the initial attack by macrophages incapable of destroying the bacillus?

A

The cell wall lipids of M. TB block fusion of phagosomes and lysosomes

20
Q

How is it ultimately destroyed?

A

Macrophages initiate a cell-mediated IR that eventually contains the infection. As tubercle bacilli multiply, infected macrophages degrade the mycobacterium and present their antigens to T-lymphocytes. Sensitized T-lymphocytse stimulate macrophages to increase concentration of lytic enzymes and ability to kill mycobacteria.

21
Q

Ghon focus?

A
  • Grey- white, granulomatous lesion
  • contains the tubercle bacilli, modified macrophages, and other immune cells
  • located in sub pleural area of the upper segments of the lower lobes or lower segments of the upper lobe
22
Q

Ghon complex?

A
  • combination of the primary lung lesion and lymph node granulomas
  • eventually heals, undergoing shrinkage, fibrous scarring, and calcification
23
Q

Latent TB?

A
  • T-lymphocytes and macrophages surround the organism in granulomas that limit their spread
  • W/ this, you do not have active disease and cannot transmit the organism to others
24
Q

What can latent TB develop into?

A

Secondary TB

25
Q

Primary TB?

A
  • form of disease that develops in previously unexposed and therefore unsensitized people
  • initiated as a result of inhaling droplet nuclei that contain tubercle nuclei
26
Q

Secondary TB?

A
  • Represents either reinfection from inhaled droplet nuclei or reactivation of a previously healed primary lesion
  • occurs in situations of impaired body defense mechanisms
27
Q

What are the 2 screening tests for TB?

A
  1. tuberculin skin test

2. chest radiographic study

28
Q

Tuberculin Skin Test?

A

Measures delayed hypersensitivity that follows exposure to the tubercle bacillus

29
Q

Anergy?

A

False negative test occurs d/t immunodeficiency states that result from HIV infection, immunosuppressive therapy, lymphoreticular malignancies, and ageing.

30
Q

How is anergy overcome?

A

It is overcome by using IGRA’s

31
Q

what does IGRA stand for?

A

Immunologic interferon-gamma release assay

32
Q

What are the diagnostic approaches for active pulmonary TB?

A
  1. Identification of the organism from cultures (may take 8 weeks)
    OR
  2. Identification of the organism from deoxyribonucleic acid or RNA amplification techniques (genotyping)
33
Q

How is TB an unusual disease?

A

It is unusual in that chemotherapy is required for a relatively long period

34
Q

Explain why treatment is challenging and how it is overcome.

A

Treatment of active TB requires the use of multiple drugs. The tubercle bacillus is an aerobic organism that multiplies slowly and remains relatively dormant in oxygen poor caseous material; it undergoes a high rate of mutation and tends to acquire resistance to any one drug-> multiple drug regimens are used for treating persons with active TB

35
Q

Identify the 2 pt groups that meet the criteria for antimicrobial therapy.

A
  1. Persons with active TB
  2. Those who have had contact with cases of active TB and who are at risk for development of an active form of the disease.
36
Q

Explain when prophylactic antimicrobial therapy is necessary.

A

Prophylactic antimicrobial therapy is necessary when persons who are infected with M. TB do not have the active disease.

37
Q

List the drugs that are used to treat active TB.

A

Isoniazid, Rifampin, Pyrazinamide, Ethambutol, FLuroquinolones, Streptomycin

38
Q

MOA of Isoniazid?

A

Combines with an enzyme needed by the INH-susceptible strains of the tubercle bacillus

39
Q

MOA of Rifampin?

A

Inhibits RNA synthesis in the bacillus

40
Q

MOA of Pyrazinamide and Ethambutol?

A

Known to inhibit the growth of tubercle bacillus

41
Q

MOA of fluroquinolones?

A

Target the mycobacterial DNA enzymes preventing replication

42
Q

Which drug is considered to by the second line drug?

A

Fluroquinolones

43
Q

When is streptomycin used?

A

Primarily used in persons with severe, possibly lifethreatening forms of TB

44
Q

What is the name of the vaccine used for TB?

A

Bacillus Calmette-Guerin vaccine (BCG)

45
Q

Use of the BCG vaccine?

A

used to prevent the development of TB in persons who are at high risk for infection

46
Q

Can you give a pt with a positive skin test result the vaccine?

A

NO, only used for pts with negative skin test results

47
Q

Limitations of the vaccine?

A

Routine use not recommended because of low prevalence of TB infection

Patho Midterm 2 (21 decks)

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