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26 Cards in this Set
- Front
- Back
What 2 main pt populations do you see Mycobacterium TB? |
immigrants and HIV pts |
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In what population does immediate progression to active TB usually occur? How does it initially present? |
kids -> presents as meningitis |
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How long does it take to detect M. tuberculosis using traditional means of identifying on solid growth media? |
3-4 wks (due to TB's long generation time of 24 hrs) |
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What are the 2 more recent means of identifying M. tuberculosis from a culture? |
1) Radiometric Growth Detection - bacteria metabolize radiolabeled palmatic acid to CO2 -- days until result
2) Gene probes - for 16s RNA - hrs until result |
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How long after exposure to TB does it take for a PPD test to turn (+)? |
3-12 weeks (this is the amount of time it takes cellular immunity to ramp up a response) |
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What is the drug of choice for latent TB? |
Isoniazid for 9 mths w/ monthly monitoring for hepatitis |
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How does mycobacteria evade host defense systems? |
intracellular growth in macrophages |
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What percent of pts infected with TB will progress to active TB sometime during their lifetime? |
15% - occurs during times of stress or immunocompromization |
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Strict Cut-off induration interpretation of PPD |
15 mm - for non-high risk populations |
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Intermediate Cut-off induration interpretation of PPD |
10 mm - for kids, immigrants, IV drug users, lab workers, illness, or converter (someone w/ and increase in induration of 10+ mm w/ in 2yr) |
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Low Cut-off induration interpretation of PPD |
5 mm - for people w/ recent TB contact, fibrotic changes on X-ray, or immunosuppressed (HIV or organ transplant) |
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"Booster Effect" |
individual was infected w/ TB a long time ago and their cellular-immunity has now waned causing their PPD test to fall below normal cut-offs. A new PPD test will boost their immunity against TB and cause a much larger response on the following test (Why you must repeat PPD 1 week after initial test) |
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How should you treat active TB? |
Start on a multi-drug regime (usually 4 - one being isoniazid). If pt fails to respond, always add more than one drug at a time to prevent selection for drug resistant strains |
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Effect of BCG vaccine on PPD test |
Causes a false + that fades w/ time. If pt has had vaccine ask if they've had PPD - if they have and it was (-) then you can assume BCG effect has waned. If you get a + result, treat as a normal + workup |
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CDC control measures for TB infected pts |
1) trx pt (most important measure) 2) Neg-pressure room isolation 3) healthcare workers wear masks
Continue precautions until there are no Acid-fast bacilli in sputum for 3 consecutive days and symp resolve |
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Mycobacterium leprae |
Acid fast bacillis that lives in cool temp places on body. Spread via armadillo-to-human contact
Use phenolic glycolipid to live intracellular in macrophage, and lipoarabinomannan to prevent T cell proliferation |
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Int. Leprosy |
very low # of AFB, hypo-pigmented skin patches, good recovery |
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Tuberculoid Leprosy |
Few # of AFB, well-defined lesions w/ some nerve involvement
Due to robust Th1 response against infected macrophages |
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Lepromatous Leprosy |
Many AFB, disfiguring nodules, nerves involved to cause sensory loss
Due to Th2 helper cells making Ab's that are useless against intracellular pathogen |
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Borderline Leprosy |
Mix of tuberculoid and lepromatous leprosy. Most of pts |
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Trx for Mycobacterium leprae and 2 trx reactions that may occur |
Dapson w/ either Rifamp or Clofazimine
1) Type 1 Reversal Rxn - increased inflammation at lesions and nerves 2) Type 2 Erythem nodosum Rxn - increase in cellular immunity in lepromatous pts causes mass cytokine release that cause inflam & papules *both rxns treated w/ steroids |
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Which species of mycobacteria are contagious? |
M. tuberculosis and M. leprae. All others are not contagious and only contracted from environment!! |
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Photochrome Non-TB Mycobacterium |
*slow growers (2+ wks) that make orange pig when light is shined on them
. M. kansasii - common in midwest (kansas!), look like beaded bacilli, lung infections in immunocomp.
. M. marinum - painless/ulcerating papule after a cut is contaminated w/ salt water |
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Scotochromes Non-TB Mycobacterium |
*slow growers (2+ wks) that make orange pig.
. M. gordonae - cause infections in immunocomp when they drink contaminated tap water |
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Nonchromogenes Non-TB Mycobacterium and their trx |
*slow growers (2+ wks) w/ no pig.
. M. avium-intracellare - most common NTM! Cause a lung infection that's similar to TB in symp and on X-ray. Can disseminate in AIDS pts w/ CD4 < 50
Trx = Clarithromycin and azithromycin |
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Rapid Growing Non-TB Mycobacterium |
*look like diphtherioids on Gm stain, cause cutaneous infections after trauma or surgery
Include: M. abscessus, M. fortuitum, M. chelonae |