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15 Cards in this Set
- Front
- Back
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Describe the physiological attributes of Mycobacteria
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acid fast rods, aerobic, non spore forming, non motile, cell wall rich in lipid content
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Are mycobacterium slow growers or fast growers?
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both, slow growers take 10 days- 8 weeks to grow, rapid growers have visible colonies in less than 7 days
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Who is at risk for tuberculosis?
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Close contacts w/ ppl w/ TB, persons with HIV, prisons, health care workers, high risk minority populations
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What is contained in the cell wall of M. tuberculosis?
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Mycolic acids - C78-C90
Wax D - high molec weight phospholipid Phosphatides - play a role in necrosis |
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How are mycobacteria stained? Describe the method.
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Acid-fast - ziehel neelsen procedure
1. cover heat fixed dried smear w/ filter paper 2. apply 5-7 drops of carbolfuchsin 3. heat slide over steam bath, do not allow to dry 4. Remove filter paper, rinse, decolorize for 2 min w/ R-OH 5. counter stain with methylene blue cells will be red, bg will be blue |
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What are the considerations of pathogenesis for m. tuberculosis?
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induced delayed hypersensitivity
Cord factor- trehalose mycolate sulfatides- prevent act of mphage LAM- prevent act of mphage Heat shock protein Cell surface antigen- prevent mphage killing |
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Describe primary tuberculosis
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Inhalation of strain, T-cell mediated resp induces hypersensitivity. microbe is phagocytized and transported to lymphnodes, but mphage unable to destroy. microbe multiplies and spreads through blood and lung, forms a calcified scar in lung w/ lymphnode, this is called a Ghon complex
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Describe secondary disseminated TB
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individual becomes reinfected or reactivated, these granulomas occur in lungs and fail to contain the spread of TB. A caseous necrosis and cavities rupture, resulting in dissemination of microbe. (miliary TB)
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What are the symptoms of TB?
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fatigue, fever, weight loss, chronic cough, purulent sputum, night sweats
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Describe the Tuberculin skin test
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1. inject 5 tuberculin units of PPD into skin
2. after 48 hrs, measure diameter of induration (hard area) >10 mm = TB <10 mm = weak or doubtful (PPD is a purified cell wall protein from M. TB) |
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What is the treatment for TB?
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Rifampin- inhibits RNA synthesis
Ethambutol - interferes w/ RNA & mycolic acid syn Isonioazid - inhibits mycolic acid syn |
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What are the forms of drug resistant TB?
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MDR-TB (resistant to 2 or more drugs)
XDR-TB (resistant to isoniazid, rifampin, fluroquinolone, and kanamycin) |
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What is the BCG vaccine made of?
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avirulent strain of M. bovis
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How is M. tb diagnosed in the lab?
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Culture on a Lowenstein-Jensen slant, gather from morning sputum.
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Identification tests for m. tuberculosis
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Slow grower
Pigment: - Niacin: + Nitrate: + Tween 80: - 68 C catalase: - Urease: + |
