Tuberculosis Flashcards
What is a latent TB infection?
person that is infected with TB but does not have active dz
What is the number 1 or 2 killer by infectious dz in the world?
TB
what percentage of the population was affected by TB in the 1800’s?
20%
Why was TB declining at a constant rate in the 1900’s and then in 1984-1994 there a stop in decline? (5)
- HIV
- Decreased public health infrastructure
- Increased immigrants
- Nosocomial outbreak
- DRTB
What happens in stage 1 of TB pathogenesis? What are the different outcomes during this stage?
ingestion of TB by resident alveolar macrophage
- phagosome-lysosome ingestion (MTB killed)
- apoptotic death (MTB killed)
- Multiplication of MTB leading to necrotic death of macrophage and MTB survive
what happens in stage 2 of TB pathogenesis?
symbiotic stage
- MTB multiplies within macrophages and incoming monocytes are reservoir
What happens in stage 3 of TB pathogenesis?
migration of T cells to site of infection leading to granuloma formation which prevents MTB from replicating
What happens in stage 4a of TB pathogenesis?
Latent TB infection (LTBI)
- MTB infection contained in granuloma and any that escape are eaten by macrophages
What happens in stage 4b of TB pathogenesis?
decline in immunity leading to reactivation of TB
- HIV or other immunocompromised individuals leads to liquifying necrosis resulting in rupture of granuloma leading to infection
what type of necrosis results in granuloma rupture?
liquifying necrosis
What are the 2 radiographic features of a latent TB infection?
Ranke complex
- Ghon complex + calcified regional hilar and/or mediastinal lymph nodes
Ghon complex
- calcified lung nodule at the site of initial infection
What will the CXR of an active TB infection show?
cavitation
diffuse infiltrates
What will sputum smears and cultures in LTBI show compared to active TB?
LTBI cultures will be negative and active will be positive
True or False: latent TB infection is asymptomatic
True
what types of symptoms do patient’s with active TB infection demonstrate?
cough
fever
night sweats
weight loss
Which type of TB is considered infectious?
active TB before treatment
Which form of TB infection will show a positive PPD?
both active and LTBI are positive
Which types of patients are considered to have a positive TB skin test with >5mm induration?
- recent close contact with active TB case
- HIV +
- organ transplant
Which types of patients are considered to have a positive TB skin test with > 10 mm induration?
immigrants from increased prevalence of TB infections
Which types of patients are considered to have a positive TB skin test with >15mm induration?
- all others even if they are at low risk for contracting
What are reasons for a false-positive on a PPD?
pt with BCG vaccine
individuals infected with environmental mycobacter
What are reasons for a false-negative on PPD?
T-cell depleted individuals
AIDS
organ transplant
What are the characteristics of a BCG vaccine and how is it different from small pox vaccine?
raised area on the deltoid. Small pox vaccine is wide and flat
What are the 2 types of IFNy release assays?
Qunatiferon
T-spot TD
Which IFNy release assay is more sensitive in immunocompromised patients and why?
T-spot more sensitive than quantiferon in immunocompromised patients because can detect single cells
True or False: The more positive a TB skin test, the more likely you are to develop a LTBI
True
Which types of patients are most at risk for reactivation of LTBI?
smokers
advanced HIV
What type of infection is responsible for 1/3 of all deaths in HIV patients?
TB
When do most TB infections happen in immigrants and why?
5 years after immigration
this is because in native land they have a lot of sun and therefore a lot of vitamin D. They mostly move to darker areas and VITAMIN D IS SHOWN TO SUPPRESS TB
What is the proposed mechanism of why vitamin D suppresses TB?
vitamin D induces production of catheliocidin which is an anti-microbial peptide that kills TB
What is the standard treatment for LTBI?
9 months of isoniazid (INH)
What is a common alternative to isoniazid and for how long?
Rifampin daily for 4 months
What is the major risk factor for INH?
hepatitis
What is 3 HP and what are the the advantages and disadvantages?
INH + Rifapentene ONCE WEEKLY for 3 months
advantages are that its a shorter course
disadvantages are that if you miss one dose, it has more drastic detrimental effect
how do you treat a patient with an active infection?
treat with multiple drugs so that it doesn’t become resistant
