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59 Cards in this Set
- Front
- Back
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What causes tuberculosis?
-Gram stain morphology -Cell wall component -Special stain -Transmission |
Mycobacterium tuberculosis
Weakly gram pos bacilli Mycolic acid Acid fast Airborne droplet transmission |
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What is the chance of infection in close contacts?
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30%
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What is the prevalence of TB?
How many new cases per year? How many deaths per year? |
Prev: 1.7 billion
Incidence: 8-10 million/year Deaths: 3 million / year |
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What is the incidence of TB in the U.S.?
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16000 new cases per year
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Why is it important to be concerned about TB?
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It is the 2nd most common infectious cause of death worldwide.
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What happened between 1953-1984?
What happened between 1985-1993? |
'53-84 TB went down to ~5%/year
'85-93 it went back up to 20% |
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Why is TB on the rise?
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Because Multidrug resistant TB is developing
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What is MDR TB?
Why is it so bad? |
-TB that is resistant to 2/more antibiotics.
-It has a very high rate of mortality and transmission |
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What is the main predisposing factor associated with contracting TB?
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Immunosuppression
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What is mainly involved in the pathogenesis of TB?
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Cell mediated immunity and the development of hypersensitivity
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What is the difference between infection and disease related to TB?
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Infection: just the organism being PRESENT in the host
Disease: the organism actually causes illness via immune response |
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What is the chance of an infected person developing disease?
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5-10%
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What individuals have a greater chance of developing disease upon TB infection?
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Immunocompromised
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What are the key inflammatory cells in the pathology of TB?
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-Macrophages
-Th1 lymphocytes |
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How does M. tb survive within macrophages?
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Inhibits phagolysosomal fusion
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Where does M. tb replicate?
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In macrophages in lung alveoli
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When is the immune response developed after M. tb infection?
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~3 weeks later
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What do the Th1 cells that respond to M. tb ingested by macrophages produce? What is the result of it?
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IFN-y - results in phagolysosome fusion in macrophages; NO production; killing of the bug.
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What do activated macrophages produce?
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TNF-alpha
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What is the function of TNF alpha?
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Recruitment of monocytes to transform into epithelioid histiocytes
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What do the epithelioid histiocytes do?
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Form granulomas to wall off M. tb
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What gene mutation prevents proper killing of the bacteria? What is the effect?
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N-RAMP1 - effect is bacteremia, miliary tb and seeding of multiple organs
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What type of necrosis is seen in the center of an epithelioid granuloma?
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Caseous necrosis
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What is the caseious necrotic center and granuloma surrounded by?
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Sensitized Tcells
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When is the Tuberculin PPD test positive?
What does the test fail to tell you? |
2-4 weeks after infection
Fails to tell you whether the person is just infected, or also diseased. |
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List 2 causes of false + PPD:
List 2 causes of false - PPD: |
False pos: Atypical mycobacteria, BCG
False neg: Severe immunosuppression, anergy |
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How big will the ring of dermatitis be in a positive test result? If immunocompromised?
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Normal pos = 10 mm
Immunocompromised pos = 5 mm |
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What type of disease is caused in a previously unexposed person? What are symptoms?
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Primary TB
-often asymptomatic -low grade fever/cough -fairly good control (90%) |
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What will be seen on the CXR in primary TB? Where in the lung?
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Ghon focus - a 1-2 cm nodule with central caseous necrosis
-See in posterior upper lobe |
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What is a Ghon complex?
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Hilar lymphadenopathy
+ Caseous necrosis in a ghon focus |
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What does the presence of a ghon complex indicate?
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Dissemination of the TB to the lymph nodes
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What are the 2 potential things that can happen to TB lesions?
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-Resolution and healing with normal tissue
-Healing with fibrosis and calcification |
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What happens to the TB organisms when fibrosis and calcification occur?
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They remain viable
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What is a calcified Ghon complex called?
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Ranke complex
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What allows progressive primary TB to develop? In what patients?
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Decreased cell mediated immunity
-Children -Elderly -Immunocompromised |
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What disease does progressive primary TB resemble?
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Acute bacterial pneumonia
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Where in the lungs is progressive primary TB seen?
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Lower/middle lobes
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What are 2 possible complications of progressive primary TB?
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-Pleural effusion
-Dissemination |
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What causes secondary TB to develop?
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Weakening of the immune system in a previously sensitized host
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What re the 2 ways that secondary TB can arise? Which is more common?
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-Reactivation (most common)
-Reinfection |
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What are the symptoms of secondary TB like compared to primary?
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Worse - fever, night sweats, fatigue, anorexia, hemoptysis
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What is less common in secondary TB than in primary?
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-Hilar lymphadenopathy
-Bacteremia |
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Where in the lungs is Secondary TB seen? What do the lesions look like?
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In the APEXes
Lesions coalesce and expand |
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What is the worst outcome of progressive secondary TB?
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-Erosion of blood vessels
-Erosion of bronchi Conversion to systemic dissemination and miliary TB |
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What are the 2 types of miliary TB?
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-Pulmonary (localized seeding throughout the lungs)
-Systemic (seeding of multiple organs) |
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What are distinguishing features of Pulmonary Miliary TB and Endobronchial, Endotracheal, or Laryngeal TB?
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-Pleural effusions
-Tuberculous empyema |
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Where does seeding occur to allow for systemic miliary TB to develop?
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Pulmonary venous return
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What is the morphology seen in systemic miliary TB?
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Numerous small gray-white nodules in affected organs.
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What is the most frequent form of extra pulmonary TB? What will be the presenting symptom?
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Lymphadenitis
-present with cervical lymph node enlargement |
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What are the 4 easiest ways to diagnose TB?
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1. H and P
2. Chest XRay 3. PPD skin test 4. Sputum direct smear for AFB |
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How is active versus latent TB differentiated?
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Via CXR
-See granulomas in active -None in latent |
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What is the gold standard for diagnosing TB?
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Sputum culture
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What is the most rapid way to diagnose TB?
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PCR
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What disease makes patients prone to acquiring TB?
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HIV
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What type of TB will HIV patients get if they are only mildly suppressed and have Th cell counts >300?
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Secondary TB
-w/out extrapulmonary involvement |
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What type of TB will HIV patients get if they are more severely suppressed and have Th cell counts <200?
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Progressive Primary TB
-w/ more extrapulmonary involvement |
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What are the 3 hallmark differences in how TB will present in an HIV+ person?
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-Sputum smear will be negative
-PPD will be false negative -Granulomas will NOT be seen in tissue |
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Why are the tests neg for a person with HIV and TB?
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Because they lack the immune response
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What are the 5 common antibiotics used to treat TB?
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-Rifampin
-Isoniazid -Pyrazinamide -Ethambutol -Streptomycin |
