Flashcards in TB Deck (46)
How is TB spread?
human to human via aerosols from coughing
T or F. Everyone that becomes infected by MTB develops disease
F. 90% do not
acid-fast bacillus, obligate aerobe that grows VERY slowly (thus, cultures take up to 6-8 weeks)
How does primary TB infection present?
most are asymptomatic (only evidence of infection is fibrocalcific nodules at the site of infection)
How does secondary TB infection occur?
viable organisms can remain dormant for years and reactivate
Secondary infection usually involves what part of the lungs?
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
Virulence factors of MTB?
-sulfatides (surface glycolipids that inhibit phagolysosomal fusion once inside macrophages)
What does cord factor do?
inhibits macrophage maturation and induces TNF-a release (virulent strains grow in a cord-like pattern)
Where does MTB reside in the body?
inside alveolar macrophages (antibodies and complement ineffective)
What polymorphism promotes for bacteremia of MTB?
When do granulomas begin to appear following TB infection?
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
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
What are the risk factors for TB?
What diseases predispose a patient to Tb risk?
DM, Hodgkin lymphoma, CKD, immunosuppression
What is Miliary TB?
lympho-hematogenous disseminated Tb (BM, liver, spleen, etc.). Can follow **primary** OR secondary TB
HIV patients at high risk
What is 'progressive' primary TB?
Tb that produces symptoms (roughly 10%)
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
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
What does progressive primary TB resemble?
acute bacterial pneumonia.
CXR of primary progressive TB?
What is characteristic of military TB upon CXR?
What are some complications of miliary TB?
-hematuria, proteinuria, sterile pyuria
What is Pott's disease?
Other complications of Miliary TB?
-pancytopenia (fom BM involvement)
How is TB diagnosed?
-acid fast sputum stain
-culture (takes 3-6 weeks)
What agar is needed to culture TB?
Lowenstein-Jensen agar (will not grow on BAP) OR
culture in liquid media (shows in 2 weeks)
When should TB treatment be initiated?
When TB is suspected, do not wait for confirmed diagnosis- start treatment