12.3: Myobacteria

Question 1

What is leading cause of death among HIV positive people in Africa?

Answer 1

• TB
• Immunosuppression leading to increased mortality
• 10% of aids patients who are infected develop disease each year
• Over 5 years if not treated for latent infection 50% develop disease

Question 2

How many people in world are infected with TB?

Answer 2

• 1/3

- 9M new cases a year

Question 3

Who are most of the people presenting with new cases of TB in america?

Answer 3

• Recent immigrants
• 70%
• Factors such as HIV

Question 4

% of people infected with TB that develop disease in lifetime?

Answer 4

7 - 10%

Question 5

How is it determined if you are infected with TB?

Answer 5

Positive skin test

Question 6

of people in America INFECTED with TB?

Answer 6

• 10M

- Only 7 - 10% of these will develop disease in LIFETIME

Question 7

How is TB transmitted?

Answer 7

• Human to human via aerosol drops

- Milk before it was pasteurized: GI TB

Question 8

Who is likely to contract TB?

Answer 8

1. Close contacts of infected person
2. Immigrants
3. Underserved
4. IV Drug users
5. Immunocompromised

Question 9

Who is most likely to progress from infection to disease?

Answer 9

1. HIV positive: low CD4 count
2. Infected w/in last 2 years
3. Babies / elderly
4. IV drug use

Question 10

How does TB travel in body?

Answer 10

• Inhaled and eventually moves to regional lymph node where it becomes bacteremic
• Allows TB to move to other parts of the body
• Usually not transmitted in blood born stage however can cause extrapulmonary TB

Question 11

Negative effects of immune response to TB?

Answer 11

• Fibrosis and holes in lung

- Host defense causes the damage

Question 12

Immune rxn with TB?

Answer 12

• Macs eat TB, digest and display in MHC to T cell
• T cell becomes primed or activated if has seen before
• Release cytokines that is protective and destructive

Question 13

2 outcomes of primary TB?

Answer 13

1. 90% have latent TB infection

2. 10% to active TB mostly people with AIDS

Question 14

What is secondary TB?

Answer 14

• Reactivation of latent TB that spread during bacteremic phase
• 80% is in upper lung
• 15% of time it reactivates in extrapulmonary site
• Disease is waiting for opportunistic time to come out of latency when you are older or immune system is depressed

Question 15

What does TB form on histology?

Answer 15

• Granulomas with giant cells surrounded by epithelial cells and central necrosis

Question 16

What type of lung disease is TB referred to as?

Answer 16

Cavitary

Question 17

How is TB diagnosed?

Answer 17

CXR with upper lung infiltrates and cavitation

Question 18

Why is the hung back of notre dame hunched of?

Answer 18

Extrapulmonary TB of the spine

Question 19

Does pulmonary TB present alongside extrapulmonary?

Answer 19

Not always

Question 20

DDx in TB?

Answer 20

1. Non TB mycobacterial infection

2. Fungal infection

Question 21

What is PPD Skin Test?

Answer 21

• Intradermal inoculation of TB antigens

- If rxn results in lump in skin from CD4 cells, it means body has seen TB before

Question 22

What is quantiferon assay?

Answer 22

• Similar to PPD but done in test tube
• If enough interferon gamma cytokine is produced it means body has seen TB
• INF gamma is what is causing the bump in the skin test

Question 23

What is AFB?

Answer 23

• “Acid fast Bacilli” smear

- Performed on sputum to test for TB

Question 24

What is NAAT?

Answer 24

“Nucleic acid amplification test”

- Take positive smear specimen and amplify in PRC like mechanism so you dont have to wait for culture to grow

Question 25

What is auramine rhodamine fluorescence?

Answer 25

• Similar to acid fast test for TB but is easier to see if positive
• IF positive move on to NAAT to see if TB or not TB

Question 26

What is non TB mycobacterium?

Answer 26

• Environmental pathogen impacted predisposed hosts
• Is a bioaerosol just not from human: soil or water
• NOT human to human transfer as in TB

Question 27

TB or NTBM more pathogenic?

Answer 27

TB

Question 28

Predisposing factors for NTBM?

Answer 28

Lung abnormalities:
1. COPD
2. Bronchiectasis
Etc

Question 29

Does NTM have latent period?

Answer 29

No

Question 30

Does NTM move outside lung?

Answer 30

No, except in AIDs

Question 31

Skin testing and quantiferon work on NTM?

Answer 31

No

Question 32

Does extrapulmonary TB cause granuloma at those sites?

Answer 32

Yes

Question 33

Next step after positive skin test?

Answer 33

CXR

Question 34

Do you treat latent TB?

Answer 34

Yes, dont want them to be the 7% that gets active and infects active population