TB Flashcards
What is the pathogenesis of a TB infection?
- inhaled bacilli are ingested by macrophages
2. bacilli replicate within macrophage, kill it, and spread hematogenously upon release
How is a TB infection contained by a normal immune system?
via cell-mediated macrophage and lymphocyte response; granulomas develop in involved tissues and wall off persistent mycobacterium
Reactivation TB occurs if:
immunity wanes in future (after granuloma formation) due to HIV, infection, steroids, immunosuppressants, cancer, etc
Persons likely to have been infected recently:
“external”
- close contact
- tuberculin conversion within 2 yrs
- new immigrants from areas of high TB prev
- residents/employees of prisons, NH, etc
- exposed health care workers
- HIV (+)
- IV drug users
- kids exposed to high-risk adults
Who should be screened for TB?
Persons likely to have been infected recently
Persons in conditions that increase risk of progression from latent to disease state
Medical Conditions of High Risk for TB
- Diabetes mellitus
- Silicosis (*destroys macroph)
- Prolonged corticosteriod therapy
- Other immunosuppressive therapy
- Cancer of the head and neck
- Lymphomas and Leukemias
- Organ transplant recepient
- End-stage renal disease
- Intestinal bypass or gastrectomy
- Chronic malabsorption syndromes
- Low body weight: >10% below the ideal
Pulmonary TB symptoms
cough fever night sweats weight loss hemoptysis
Pulmonary signs of TB
Cachexia
Signs of consolidation
Rales: crackles
Advanced: respiratory failure
Extra-pulm signs of TB
Renal- pyurea
Meningeal- fever, neck stiffness, coma
Bony- Potts Disease, neuropathies
Scrofula- cervical lymphadenitis (WTF did I misspell?)
(EXTRa PuLM = extremities (bony/neuropathy), pyurea, lymphadenitis, meningitis)
In (+) IGRA test, T cells of individuals infected with MTB produce ____ when exposed to…
interferon-gamma
the MTB antigen
What is a strength of IGRA testing?
more sensitive than TST
more specific than TST
do not have to return to clinic to get results
What tests can be used for detecting latent tuberculosis infection?
TST or the interferon-gamma release assay
In USA, most reported cases of TB have:
abnormal chest radiograph
What 2 signs are more common in primary TB?
Adenopathy and pleural effusion
What is more common in reactivation TB?
Apical disease and cavities
What can be seen with both reactivation and primary TB? What does this signify?
Miliary TB
ICH
The gold standard of TB diagnosis:
culture-isolation of MTB with sputum (preferably spontaneously expectorated)
The five commandments of diagnosis of
Tuberculosis:
Suspect the disease from demographics Culture appropriate specimens Obtain Chest X-ray PPD skin test Examine (symptoms and signs)
=SCOPE
1st line TB drugs (6)
- Isoniazide
- Rifampin
- Pyrazinamide
- Ethambutol
- Rifabutin
- Rifapentine
(“RIPE”)
2nd line TB drugs
- Amikacin
- Kanamycin
- Capreomycin
- Ethionamide
- Fluoroquinolones
Patients are no longer considered infectious
if…
On adequate therapy with multiple agents.
Had a significant clinical response to therapy.
Had 3 consecutive negative sputum smears.
After TB exposure, ____% will have a positive skin test. Of these, ___% will actually develop disease, but only if…
25%
10%
immunosuppressed
During the first ___ years after infection, people are at a high risk of developing TB.
2
The containment of TB in the body is the function of:
macrophages and lymphocytes
When does tuberculin conversion occur? When will a skin test be (+)?
6-10 weeks after infection
2 weeks after exposure
Where will TB likely spread in the body?
bone
brain
lungs
kidneys
The incidence of TB in the US is (increasing/decreasing)
decreasing
The current goal of TB screening is to identify:
those at high risk of developing TB from a latent infection
What is the greatest known risk factor for reactivation of latent TB?
HIV
10% risk per year of developing TB if hx of (+) skin test; 40% co-infection rate in inner city clinics
Symptoms of pulmonary tuberculosis are:
nonspecific
pulmonary
systemic
Preventive therapy for TB is mainly targeted to…
secondary prevention (infected but latent)
Acceptable regimens for latent TB infections (3):
INH daily or twice weekly x9mo
INH daily or twice weekly x6mo
Rifampin daily x4mo
T/F: If a drug is failing in TB trx, add another abx.
F! bad for resistance
Regiments for active TB infections:
PZA or EB x2mo
INH or RM x6mo
(is this right? I was confused)
