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17 Cards in this Set
- Front
- Back
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What can cause a false positive PPD?
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Bacillus calmette Guerin(BCG) vaccine, prior treated tbc(once exposed, the PPD remains positive even after treatment, exposure to nontbc mycobacteria.
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How is M. tbc cultured?
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In C(14) labeled palmitic acid broth with growth detected by release of CO2. Samples can also be cultured on Lowenstein-Jensen agar, but results take weeks.
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How is tbc transmitted?
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Inhalation of infected respiratory droplets.
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What is primary tbc?
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An infection in the lungs of a previously unexposed individual.
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Describe the pathogenesis of primary tbc?
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Mycobacteria ingested by phagocytes trigger cell mediated immunity leading to caseating granulomas.
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What is the result of most primary infections with tbc?
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No symptoms(asymptomatic 90% positive PPD, Ghon complex
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What groups are at risk for symptomatic primary tbc?
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Those with deficient cell mediated immunity(children, elderly, immunocompromised or immunosuppressed).
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What is the pathology of symptomatic primary tbc?
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In the lungs and other organs, large caseous granulomas develop and eventually, liquefy, creating cavitary lesions with air filled levels(air fluid levels in lungs only)
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What is a Ghon complex?
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Ghon complex=Ghon focus(calcified nodule in the middle or lower lung)+ a calcified hilar lymph node.
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What is secondary tbc?
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Reactivation of a prior infection infection due to weakened immunity(months to years later). Most adult cases of active tbc are secondary.
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What are the signs and symptoms of active pulmonary tbc?
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Cough with hemoptysis, low grade fever, night sweats and weight loss. Chest X ray showing upper lobe infiltrates, cavitary lesions, calcifications.
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What is the treatment for active tbc?
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6 months regimen: initially 4 drugs(rifampin, isoniazid, pyrazinamide, ethambutol) for 2 months, followed by 4 months of isoniazid and rifampin. Multiple drugs should always be used to prevent the emergence of multidrug resistant strains.
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What percentage of primary infections progress to active tbc?
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5% of those primarily infected will develop reactivation tbc in the first 1-2 years. Another 5 % will develop reactivation sometime later in life.
Normal infected individuals have a 10% lifetime risk of active infection, while immunocompromised patients are at higher risk. |
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What is miliary tbc?
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Disseminated infection leading to millet seed sized granulomas in lungs, liver spleen, bone, kidneys, spine and other organs.
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Who gets miliary tbc?
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Those with weakened cell mediated immunity(HIV positive, elderly and children).
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What is Pott's disease?
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Tbc infection of the thoracic/lumbar spine leading to destruction of intervertebral discs/bodies and compression fractures.
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What is the most common extrapulmonary manifestation of tbc?
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Scrofula or cervical mycobacterial lymphadenitis.
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