Flashcards in TB Deck (46):
1
How is TB spread?
human to human via aerosols from coughing
2
T or F. Everyone that becomes infected by MTB develops disease
F. 90% do not
3
Describe TB
acid-fast bacillus, obligate aerobe that grows VERY slowly (thus, cultures take up to 6-8 weeks)
4
How does primary TB infection present?
most are asymptomatic (only evidence of infection is fibrocalcific nodules at the site of infection)
5
How does secondary TB infection occur?
viable organisms can remain dormant for years and reactivate
6
Secondary infection usually involves what part of the lungs?
apices
7
How does the mycolic acid of the cell wall of MTB promote infection?
Mycolic acids, glycolipids, arabinagalactans, and free lipids make the cell wall impermeable to many host systems
8
Virulence factors of MTB?
-cord factor
-sulfatides (surface glycolipids that inhibit phagolysosomal fusion once inside macrophages)
9
What does cord factor do?
inhibits macrophage maturation and induces TNF-a release (virulent strains grow in a cord-like pattern)
10
Where does MTB reside in the body?
inside alveolar macrophages (antibodies and complement ineffective)
11
What polymorphism promotes for bacteremia of MTB?
NRAMP1
12
When do granulomas begin to appear following TB infection?
3 weeks
13
How do granulomas form?
after TB enters macrophages, the macrophages produce Il-12 which activate TH1 cells to produce IFN-y, which then further activates them to produce TNF-a and cytokines that cause monocyte recruitment and caseous necrosis and containment of infection
14
Why are rheumatoid arthritis patients at an increased risk for TB?
because they are often treated with TNF-a antagonists, which is critical for granola formation
15
What are the risk factors for TB?
-crowded conditions
-malnourished
-alcoholism, poverty
-AIDS
-elderly
16
What diseases predispose a patient to Tb risk?
DM, Hodgkin lymphoma, CKD, immunosuppression
17
What is Miliary TB?
lympho-hematogenous disseminated Tb (BM, liver, spleen, etc.). Can follow **primary** OR secondary TB
HIV patients at high risk
18
What is 'progressive' primary TB?
Tb that produces symptoms (roughly 10%)
19
How does secondary TB present?
insidious onset of malaise, anorexia, low-grade fever weight loss, night sweats, SOB, purulent sputum, blood streaked sputum, and rarely pleuritic pain
20
What happens in progressive primary TB?
the initial infected tubercle can erode into a bronchus, spill its contents and infection then spread to other parts of the lung
21
What does progressive primary TB resemble?
acute bacterial pneumonia.
22
CXR of primary progressive TB?
-lobar consolidation
-hilar LAD
-pleural effusion
23
What is characteristic of military TB upon CXR?
millet seeds
24
What are some complications of miliary TB?
-meningitis
-Pott's disease
-N/V, diarrhea
-hematuria, proteinuria, sterile pyuria
25
What is Pott's disease?
vertebral osteomyelitis
26
Other complications of Miliary TB?
-pancytopenia (fom BM involvement)
-Adrenal insufficiency
-Epididymitis
-prostatitis
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How is TB diagnosed?
-acid fast sputum stain
-culture (takes 3-6 weeks)
-PCR
28
What agar is needed to culture TB?
Lowenstein-Jensen agar (will not grow on BAP) OR
culture in liquid media (shows in 2 weeks)
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When should TB treatment be initiated?
When TB is suspected, do not wait for confirmed diagnosis- start treatment
30
Treatment for primary/secondary TB?
-Isoniazid, Rifampin, Pyrazinimide, Ethambutol (RIPE)
31
Why is such long treatment regimen needed for TB?
-granuloma blocks ABX
-organism is slow growing
32
What is MDR TB?
resistant to INH and RIF (common in AIDs patients)
33
What is XDR TB?
resistance to INH, RIF, fluoroquinolone, and at least 1 other drug
34
How does HIV affect TB?
-increased frequency of false negative sputum smears
-absence of granulomas
-cavitation/bronchial damage less severe
35
How is latent Tb diagnosed?
-PPD (purified protein derivative)
-IGRA
36
How does a PPD work?
I.D. injection of tuberculin material which stimulates a delayed type hypersensitivity mediated by T cells (causes induration within 48-72 hrs)
37
What can cause a false positive PPD?
immunization with BCG or infection is a non-TB mycobacteria
38
How does an IGRA (Quantiferon gold Quan-TB, T-spot) work?
Patient blood cells are exposed to antigens from MTB and the amount of INF-y released is measured. (no false positive from BCG or NTM infections)
39
Latent Tb tests in HIV patients
False negatives can occur in both tests due to lack of immune response, called anergy
40
How is latent Tb treated?
INH for 9 months OR
INH and Rifapentine for 3 months
41
What determines a positive PPD?
risk factors
42
What is a positive PPD in someone with no known risk factors?
15+mm
43
What is a positive PPD in a homeless, IVDU, nursing home resident, recent immigrant, children under 4?
10-15mm
44
What is a positive PPD in a HIV, immunosuppressed, organ transplant, prior TB?
5-10mm
45
Do you measure the erythema or induration in a PPD?
induration!
46