Mycobacteria

Question 1

What proportion of the world is infected with TB?

Answer 1

1/3

Question 2

How many Americans are infected with TB and what does this mean?

Answer 2

10 million Americans are affected (based on positive skin tests- does NOT mean active infection)

Question 3

Only ____% of TB-infected people develop disease in their lifetimes, and the remainder have latent infections.

Answer 3

7-10

Question 4

Which are the main 2 groups of people who are more likely to progress to active TB disease?

Answer 4

• HIV patients

- Those who were recently infected with TB (within the past 2 years)

Question 5

Which people are at greatest risk for TB transmission?

Answer 5

close contacts (~20% will get infected)

Question 6

Is extrapulmonary TB contagious?

Answer 6

rarely!

Question 7

If you have latent TB, can you transmit it?

Answer 7

No!

Question 8

What is an airborne droplet nucleus?

Answer 8

It is when the fluid of pathogenic droplets evaporates. They are so small and light that they are susceptible to ingestion and gaining access to alveolar macrophages.

Question 9

This term describes the primary site of lung infection.

Answer 9

Ghon focus

Question 10

This term describes a calcified Ghon complex PLUS an ipsilateral calcified mediastinal lymph node.

Answer 10

Ranke complex

Question 11

Once M. Tb enters the body, how does it spread?

Answer 11

regional lymph nodes and blood

Question 12

What are the 2 outcomes of primary (initial) TB infection?

Answer 12

• Latent TB infection (90% of the time)

- Progression to active TB (mostly in HIV/AIDS patients)

Question 13

What are the 2 outcomes of secondary (reactivation) TB infection?

Answer 13

• Upper lung infiltrate/cavitation (80-90%)
• “Extrapulmonary” sites of reactivation from initial bloodborne spread of infection (ex: brain, heart, bone, GU; only 10-15% of secondary disease cases)

Question 14

How do latent TB infections heal?

Answer 14

fibrosis and calcification

Question 15

Which other infections can resemble TB due to chronic granulomatous nature?

Answer 15

• NTM infections (esp. M. kansasii)

- Fungal infections (esp. Histoplasmosis and fungal pneumonia)

Question 16

What is the definition of Nontuberculous Mycobacteria?

Answer 16

environmental pathogens that affect predisposed hosts (they are ubiquitous and usually do not cause infection in normal, immunocompetent hosts)

Question 17

What are the environmental sources of NTM?

Answer 17

• Bioaerosols
• Water
• Soil (80% of soil samples, esp. in SE U.S.)
• Nosocomail sources

Question 18

What is the common theme for predisposition to NTM lung disease?

Answer 18

underlying structural lung abnormality (COPD, bronchiectasis, previous chest radiotherapy, ILD, previous PE, recurrent aspiration pneumonia)

Question 19

What is Pott’s disease?

Answer 19

It is an extrapulmonary manifestation of TB in which TB causes osteomyelitis of the spine (lower thoracic, upper lumbar)

Question 20

Think extrapulmonary TB with __________ fluids.

Answer 20

lymphocyte-predominant

Question 21

What are the diagnostic tests for sputum of suspected TB patients?

Answer 21

• AFB smears

- NAAT (nucleic acid amplification testing - allows for rapid detection)

Question 22

Are NTM infections spread human-to-human?

Answer 22

NO!

Question 23

Do NTM infections usually disseminate outside of the lung?

Answer 23

NO, except in AIDS patients.

Question 24

True or false: PPD skin testing and Quant Gold may be used to detect NTM infections.

Answer 24

False!