Mycobacterial Infections

Question 1

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

Answer 1

**M. TB**
M. Bovis
**M. Africanum**
M. Microti
M. Canetti
M. Caprae
M. Pinnipedii

Question 2

What is atypical TB?

Answer 2

Non-TB mycobacteria that grow slowly

Question 3

What are the two bacteria that comprise the MAC complex?

Answer 3

M. Avium

M. intracellulare

Question 4

What is the natural source of non-TB bacteria?

Answer 4

Water sources

Question 5

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

Answer 5

In patients with underlying bronchiectasis or COPD

Question 6

What are the two distinct forms of MAC?

Answer 6

Fibrocavitary disease

Fibronodular disease

Question 7

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

Answer 7

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

Usually upper lobe predominance on x-ray.

Question 8

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

Answer 8

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

Diffuse interstitial infiltrates and bronchiectasis

Question 9

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

Answer 9

Water (tap water in endemic cities)

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

Question 10

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

Answer 10

false–different drugs

Question 11

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

Answer 11

White, middle aged females

Usually infiltrates–rarely cavitary lesions

Question 12

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

Answer 12

True

Question 13

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

Answer 13

True

Question 14

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

Answer 14

Macrolide + rifampin + ethambutol

12-18 months

Question 15

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

Answer 15

1 = HIV
2 = TB

Question 16

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

Answer 16

1/3

Question 17

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

Answer 17

Sub-saharan africa

Islands of southeast Asia

Question 18

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

Answer 18

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

Question 19

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

Answer 19

True

Question 20

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

Answer 20

true

Question 21

What is primary TB?

Answer 21

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

Question 22

What is a Ghon complex?

Answer 22

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

Question 23

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

Answer 23

Most aerated area of the lung

Question 24

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

Answer 24

Hematogenous spread, causing active disease. Becomes infectious.

Question 25

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

Answer 25

Pleural effusion

Question 26

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

Answer 26

1/3

Question 27

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

Answer 27

Hilar LAD Perihilar infiltrates Effusion

Question 28

What percent of patients with primary TB become asymptomatic?

Answer 28

90%

Question 29

What is the most frequent source of infection with TB?

Answer 29

latent TB

Question 30

Patients with non-active TB remain asymptomatic until when?

Answer 30

Until cell mediated immunity is compromised

Question 31

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

Answer 31

False--just been exposed.

Question 32

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

Answer 32

True

Question 33

What is involved with the TB skin test?

Answer 33

Cell mediated immunity to the PPD of TB

Question 34

What is measured with the Quantiferon gold test?

Answer 34

IFM-gamma

Question 35

How is the mantoux skin test performed?

Answer 35

Intradermal injection of 0.1 mL of PPD

Question 36

How are the results of a TB skin test documented?

Answer 36

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

Question 37

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

Answer 37

several weeks

Question 38

What may cause a false-negative TB skin test?

Answer 38

Impaired cellular immunity

Question 39

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

Answer 39

- HIV infection (immunosuppressed) - Close contact with contagious case - Abnormal CXR findings

Question 40

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

Answer 40

- Lung or kidney disease - children under 4 - Foreign - high risk setting

Question 41

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

Answer 41

Healthy individuals unlikely to get TB

Question 42

What does the quantiferon gold test involve?

Answer 42

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

Question 43

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

Answer 43

No

Question 44

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

Answer 44

Quantiferon TB gold | T. spot assay

Question 45

What is the specificity of the Quantiferon gold test?

Answer 45

95%

Question 46

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

Answer 46

true

Question 47

What is the treatment for TB?

Answer 47

Isoniazid x9 months Rifampin Ethambutol Pyrazinamide

Question 48

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

Answer 48

- Silicosis - DM - CKD - Gastrectomy

Question 49

What are the characteristics of the fever associated with TB?

Answer 49

Diurnal | Progressively worsens

Question 50

When does dyspnea occur in TB infections?

Answer 50

With significant parenchymal involvement

Question 51

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

Answer 51

Pleural involvement

Question 52

What is the usual dose of isoniazid for TB?

Answer 52

900 mg

Question 53

What are the general principles of drug therapy for TB?

Answer 53

use at least two drugs that have documented activity

Question 54

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

Answer 54

Rifabutin

Question 55

What is the main adverse effect of rifampin?

Answer 55

Orange excretions

Question 56

What is the major adverse effect of ethambutol?

Answer 56

Loss of color vision

Question 57

What are the two phases of TB treatment?

Answer 57

- 4 drugs x8 weeks | - INH and RIF for an additional 4-7 months

Question 58

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

Answer 58

- 8 weeks daily - daily x2 weeks, then BID for weeks - 3 times weekly for 6 weeks

Question 59

What is the definition of multidrug resistant TB?

Answer 59

Lab confirmed resistance to INH and rifampin

Question 60

What is the way to diagnose active TB?

Answer 60

Sputum culture