Quiz 7 - Spivak, A - TB

Question 1

What is the worldwide prevalence of TB (latent and active)?

Answer 1

33%

• 1/3 of the world is infected with TB
• *About 2 billion people

Question 2

T/F - TB is the 2nd most common infectious cause of death in adults worldwide?

Answer 2

TRUE

Question 3

T/F - TB prevalence increases with poverty and HIV infection.

Answer 3

TRUE

Question 4

Tell me about Mycobacterium TB.

Answer 4

Cell membrane of MYCOLIC ACID

-Or, ACID FAST BACILLI (AFB)

Question 5

T/F - Humans are the only known reservoir of M tuberculosis.

Answer 5

TRUE

Question 6

How is TB spread?

Answer 6

Aerosolized droplets from coughing, sneezing, talking, singing

Droplets can be suspended in air for hours

Exposure occurs from breathing in droplets

Question 7

T/F - Exogenous factors determine exposure risk.

Answer 7

TRUE

The Rnot (want this to be below 1, since if it is 2, I could infect 2 people, and those people could infect 2 people each, etc.) for TB is 20!

Factors:

• Duration and intimacy of contact
• Infectiousness of index case
• In high prevalence settings

Question 8

What are 4 outcomes of TB exposure?

Answer 8

Clearance - No infection

Latent infection - Infection w/o symptoms

Primary disease - Infection with immediate symptoms

Reactivation disease - Development of symptoms months to years after latent infection

Question 9

T/F - Endogenous factors determine risk of developing disease.

Answer 9

TRUE

Endogenous factors:

• Innate and cell-mediated immunity
• Co-morbid conditions

Question 10

T/F - Most exposed adults will have primary infection, and have 10% lifetime chance of reactivation.

Answer 10

TRUE

Question 11

What reactivates Latent TB?

Answer 11

HIV infection (100 fold increased risk)
—If you have latent TB and HIV, you have an 8-10%/year of reactivating TB

Question 12

How does the body deal with TB?

Answer 12

Macrophages (alveolar)
-However, MTB can still replicate inside the phagosome
—A granuloma results
—-This is a collection of immune cells (mostly macrophage around the TB, then T cells, then fibroblasts) that contain M TB spread

2 part response

• Macrophage activating response
• Delayed-type hypersensitivity

Question 13

Symptoms of latent TB?

Answer 13

NONE

Question 14

Active TB symptoms?

Answer 14

Pulmonary symptoms are common
-Cough, hemoptysis, lung collapse, chest pain

Wasting (Historically: Consumption)
-Fever, fatigue, weight loss, night sweats

TB can be present in any organ of the body

Question 15

Dx of LTBI?

Answer 15

Low incidence setting (like in the US)

-Target at risk populations only

Question 16

How is at high risk of exposure of TB?

Answer 16

Known TB contacts

Immigrants from endemic areas

Homeless shelters, prisons, nursing homes

Question 17

Who is at high risk of getting TB?

Answer 17

HIV infection

Endemic areas

IV use

Diabetes, silicosis

Immune suppression

Question 18

Diagnostic tests of LTBI?

Answer 18

PPD
-Skin test looking for hypersensitivity rxn

IGRA
-Expose blood cells to TB antigens in a dish, and look for IFNgamma release

Question 19

Dx active TB?

Answer 19

Exposure history, signs/symptoms, imaging

AND

Granulomas, AFB seen on smear, or on culture

Question 20

Tx of active TB.

Answer 20

RIPE

Rifampin
Isoniazid
Pyrazinamide
Ethambutol

For 2 months

AND

RI

Rifampin
Isoniazid

For 4 months

4 drugs for 2 months and 2 drugs for 4 months

Question 21

Why HIV and TB have synergy?

Answer 21

HIV most powerful known risk for reactivating latent TB

TB is most common cause of AIDS mortality

• Risk of TB reactivation is 5-8% per year in HIV co-infected pts*
• This is additive, so each year it is increased (5,10,15,20)