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28 Cards in this Set
- Front
- Back
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mycobacterium genus features
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acid fast rods
waxy cell wall OBLIGATE AEROBE - mycolic acids in cell wall w/ high lipid concentration (long chain fatty acids) |
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mycobacterial cell wall makes it highly resistant to ...
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dessication
many chemicals (NaOH) BUTT....it is SENSITIVE TO UV LIGHT |
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mycobacterial cell wall components
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polypeptides
free lipids (waxes, cord factor) arabinogalactan mycolate peptidoglycan layer cyctoplasmic membrane |
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Key vignette clues for Tuberculosis
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- high risk patient (low ses, hiv + or iv drug user)
- chronic cough, weight loss - ghon complex or focus - auramine-rhodamine staining acid fast - niacin producer , heat senstiive catalase - positive DTH test - facultative intracellular organism |
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tb distinguishing features
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- auramine-rhodamine staining bacilli (bright apple green)
- acid fast - aerobic, slow growing (weeks) on Lowenstein-Jensen medium ; palmitic acid broths are faster - niacin producer - heat sensitive catalase (68*f) |
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tb reservoir / transmission
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lungs ; respiratory droplets
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pathogenesis of tb
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- forms granulomas
- sulfatides (sulfolipids in cell envelope) that inhibit lysosome fusion = permits intracellular survival - cord factor --> inhibits leukocyte migration - tuberculin - surface protein --> responsible for DTH reaction (granulomas and caseous necrosis) - NO exotoxins, injury is due to host immune response |
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tb diseases
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primary and secondary tb
a.) primary --> replicate in macrophages (ghon focus) - macs travel to lymph nodes (ghon complex) ; most people heal w/o disease; bugs walled off in granulomas b.) reactivation --> immune sys drops(poor tcell function), granulomas erode into airways (apices of lungs) --> replication --> proceeds to ANY organ sys in body --> miliary tb |
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differential dx for tb
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a. israelli
a. fumigatus h.capsulatum atypical mycobacteria nocardia b.dermatiditis |
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tb diagnosis
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- auramine/rhodamine stain (apple green) --> if positive --> acid fast stain --> then PPD skin test ; measure induration in 48-72 hours
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what does a positive PPD indicate?
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indicates exposure but not necessarily active disease
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tb treatment
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multiple drugs are needed ; short term rx
- first 2 months--> RIP treatment - next 4 months --> INH + rifampin - ethambutol or streptomycin added if possible drug resistant case |
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tb prevention
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family members, hospital workers (need large dose to become infected) ISONIAZID for 9 MONTHS
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in the world but the u.s. , what live vaccine do they use?
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Bacille- Calmette- Guerin vaccine --> live attenuated bugs that prevent DISSEMINATED disease
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MOTTS -
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Mycobacterium Other Than Tuberculosis --> atypical, noncontagious, found in water, soil and cigs,
- use runyon terminology to divide groups ; differentiated via (carotenoid pigments after exposure to light) |
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M. leprae
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- acid fast rods from punch biopsy
- obligate intracellular parasite (cannot b cultured) - prefers cooler temps on the body (extremities) |
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leprosy reservoir
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human mucosa, skin and nerves
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leprosy transmission?
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nasal discharge from untreated pats
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how does it cause disease?
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obligate intracellular parasite; cooler parts of body
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leprosy is what type of disease?
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it is a disease of "continuum"
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leprosy vignette clues
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acid fast bacilli in punch biopsy
- immigrant patient w/ sensory loss in the extremities |
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tuberculoid leprosy traits?
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strong cmi response, + lepromin skin test , low # of tissue bugs, damage caused by CMI response --> granuloma formation --> nerve enlargement/damage --> loss of sensation
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how many lesions do u see with tuberculoid leprosy?
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macular, nerve enlargement and paresthesias
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Lepromatous leprosty traits?
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patient has a:
- weak CMI - (-) lepromin skin test b/c cannot mount a CMI response - high # of cells in tissue - nerve damage from bacterial overgrowth in the cells (loss of sensation too) - nodular lesions --> eyebrows, saddle nose, paresthesias and leonine facies |
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leprosy differential diagnosis
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leishmania
t. pallidum m. furfur |
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leprosy diagnosis
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- punch biopsy or nasal scraping
- acid fast stain - NO CULTURES |
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Leprosy Rx
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multiple drugs:
- dapsone + rifampin + clofazimine (if lepromatous leprosy) |
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leprosy prevention
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dapsone for family contacts
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