Quiz 7 - Spivak, A - TB Flashcards
What is the worldwide prevalence of TB (latent and active)?
33%
- 1/3 of the world is infected with TB
- *About 2 billion people
T/F - TB is the 2nd most common infectious cause of death in adults worldwide?
TRUE
T/F - TB prevalence increases with poverty and HIV infection.
TRUE
Tell me about Mycobacterium TB.
Cell membrane of MYCOLIC ACID
-Or, ACID FAST BACILLI (AFB)
T/F - Humans are the only known reservoir of M tuberculosis.
TRUE
How is TB spread?
Aerosolized droplets from coughing, sneezing, talking, singing
Droplets can be suspended in air for hours
Exposure occurs from breathing in droplets
T/F - Exogenous factors determine exposure risk.
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
What are 4 outcomes of TB exposure?
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
T/F - Endogenous factors determine risk of developing disease.
TRUE
Endogenous factors:
- Innate and cell-mediated immunity
- Co-morbid conditions
T/F - Most exposed adults will have primary infection, and have 10% lifetime chance of reactivation.
TRUE
What reactivates Latent TB?
HIV infection (100 fold increased risk) —If you have latent TB and HIV, you have an 8-10%/year of reactivating TB
How does the body deal with TB?
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
Symptoms of latent TB?
NONE
Active TB symptoms?
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
Dx of LTBI?
Low incidence setting (like in the US)
-Target at risk populations only
How is at high risk of exposure of TB?
Known TB contacts
Immigrants from endemic areas
Homeless shelters, prisons, nursing homes
Who is at high risk of getting TB?
HIV infection
Endemic areas
IV use
Diabetes, silicosis
Immune suppression
Diagnostic tests of LTBI?
PPD
-Skin test looking for hypersensitivity rxn
IGRA
-Expose blood cells to TB antigens in a dish, and look for IFNgamma release
Dx active TB?
Exposure history, signs/symptoms, imaging
AND
Granulomas, AFB seen on smear, or on culture
Tx of active TB.
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
Why HIV and TB have synergy?
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)
