Mycobacterial Infections Flashcards

1
Q

What are the bacteria that cause typical TB? (7) Which two are the main organisms that cause TB?

A
**M. TB**
M. Bovis
**M. Africanum**
M. Microti
M. Canetti
M. Caprae
M. Pinnipedii
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2
Q

What is atypical TB?

A

Non-TB mycobacteria that grow slowly

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3
Q

What are the two bacteria that comprise the MAC complex?

A

M. Avium

M. intracellulare

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4
Q

What is the natural source of non-TB bacteria?

A

Water sources

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5
Q

Progressive lung disease with non-TB bacteria usually occurs in whom?

A

In patients with underlying bronchiectasis or COPD

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6
Q

What are the two distinct forms of MAC?

A

Fibrocavitary disease

Fibronodular disease

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7
Q

What is the fibrocavitary disease seen with the MAC complex infection? In whom is it seen? How does it appear on CXR?

A

TB-like disease with Cavitary lesions. Seen in older male smokers with COPD.

Usually upper lobe predominance on x-ray.

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8
Q

What is the fibronodular disease seen with the MAC complex infection? In whom is it seen? How does it appear on CXR?

A

TB like disease seen in nonsmoking women over 50 yo, and without underlying lung disease

Diffuse interstitial infiltrates and bronchiectasis

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9
Q

What is the natural source of M. Kansasii? How does this present?

A

Water (tap water in endemic cities)

TB cavitary lesions with chest pain, cough, hemoptysis and night sweats

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10
Q

true or false: the drugs used to treat atypical TB are the same as typical TB, making culturing them clinically insignificant

A

false–different drugs

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11
Q

Who usually gets fast growing atypical TB infections? Are cavitations more or less common?

A

White, middle aged females

Usually infiltrates–rarely cavitary lesions

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12
Q

True or false: there is no other test besides a culture to differentiate TB from non TB

A

True

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13
Q

True and false: the ssx of atypical TB are the same as usual TB

A

True

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14
Q

What is the treatment for atypical TB (3)? How long?

A

Macrolide + rifampin + ethambutol

12-18 months

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15
Q

What is the most common infectious cause of death worldwide? #2?

A
1 = HIV
2 = TB
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16
Q

What fraction of the world’s population is infected with TB?

A

1/3

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17
Q

Where in the world are the highest rates of infection with TB?

A

Sub-saharan africa

Islands of southeast Asia

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18
Q

What are the three possible consequences of TB droplet inhalation? What is the most common?

A
  • Immediately cleared without issue
  • immediate onset of disease
  • Latent infection with reactivation years later**
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19
Q

True or false: most patients with exposure to TB clear it without issue

A

True

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20
Q

True or false: in patients who are infected with TB, most of the time is is contained

A

true

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21
Q

What is primary TB?

A

When initial infection with TB is not controlled by local defenses and spreads to regional lymph nodes

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22
Q

What is a Ghon complex?

A

Localized Lymphadenopathy in the lung that is caused by tuberculosis.The lesions consist of a calcified focus of infection and an associated lymph node

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23
Q

Why are the cavitary lesions with TB usually seen in the apices of the lung?

A

Most aerated area of the lung

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24
Q

What happens with TB infection if the cell mediated immunity is inadequate?

A

Hematogenous spread, causing active disease. Becomes infectious.

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25
Q

What is the pleuritic chest pain with TB usually associated with?

A

Pleural effusion

26
Q

What fractions of patients with primary TB have the usual ssx?

A

1/3

27
Q

What are the CXR findings of active TB? (3)

A

Hilar LAD
Perihilar infiltrates
Effusion

28
Q

What percent of patients with primary TB become asymptomatic?

A

90%

29
Q

What is the most frequent source of infection with TB?

A

latent TB

30
Q

Patients with non-active TB remain asymptomatic until when?

A

Until cell mediated immunity is compromised

31
Q

true or false: a positive TB skin tests indicates an active infection

A

False–just been exposed.

32
Q

True or false: as long as the cell mediated immunity remains intact, patients with latent TB are not a hazard to anyone else

A

True

33
Q

What is involved with the TB skin test?

A

Cell mediated immunity to the PPD of TB

34
Q

What is measured with the Quantiferon gold test?

A

IFM-gamma

35
Q

How is the mantoux skin test performed?

A

Intradermal injection of 0.1 mL of PPD

36
Q

How are the results of a TB skin test documented?

A

mm of induration–NOT erythema–perpendicular to the long axis of the forearm

37
Q

How long after infection will a skin test show a positive result for TB?

A

several weeks

38
Q

What may cause a false-negative TB skin test?

A

Impaired cellular immunity

39
Q

What are the factors that indicates a positive TB skin test with more than 5 mm of induration? (3)

A
  • HIV infection (immunosuppressed)
  • Close contact with contagious case
  • Abnormal CXR findings
40
Q

What are the factors that indicates a positive TB skin test with more than 10 mm of induration? (3)

A
  • Lung or kidney disease
  • children under 4
  • Foreign
  • high risk setting
41
Q

What are the factors that indicates a positive TB skin test with more than 15 mm of induration?

A

Healthy individuals unlikely to get TB

42
Q

What does the quantiferon gold test involve?

A

T cell release of IFN in response to the antigen specific M. TB

43
Q

Can the Quantiferon gold test determine if the infection is active or latent?

A

No

44
Q

What are the tests for patients who had the BCG infection?

A

Quantiferon TB gold

T. spot assay

45
Q

What is the specificity of the Quantiferon gold test?

A

95%

46
Q

true or false: TB abx should be given to anyone, regardless of age, if they have a positive TB skin test

A

true

47
Q

What is the treatment for TB?

A

Isoniazid x9 months
Rifampin
Ethambutol
Pyrazinamide

48
Q

What are the high risk conditions for getting TB? (4)

A
  • Silicosis
  • DM
  • CKD
  • Gastrectomy
49
Q

What are the characteristics of the fever associated with TB?

A

Diurnal

Progressively worsens

50
Q

When does dyspnea occur in TB infections?

A

With significant parenchymal involvement

51
Q

If pleuritic chest pain is present with TB, what does this indicate?

A

Pleural involvement

52
Q

What is the usual dose of isoniazid for TB?

A

900 mg

53
Q

What are the general principles of drug therapy for TB?

A

use at least two drugs that have documented activity

54
Q

What is the alternative to rifampin therapy if a patient is taking other drugs metabolized by p450 enzymes

A

Rifabutin

55
Q

What is the main adverse effect of rifampin?

A

Orange excretions

56
Q

What is the major adverse effect of ethambutol?

A

Loss of color vision

57
Q

What are the two phases of TB treatment?

A
  • 4 drugs x8 weeks

- INH and RIF for an additional 4-7 months

58
Q

What are the three alternative schedules for the first phase of treatment for TB?

A
  • 8 weeks daily
  • daily x2 weeks, then BID for weeks
  • 3 times weekly for 6 weeks
59
Q

What is the definition of multidrug resistant TB?

A

Lab confirmed resistance to INH and rifampin

60
Q

What is the way to diagnose active TB?

A

Sputum culture