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33 Cards in this Set
- Front
- Back
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How is MDR-TB defined?
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Resistance to at least INH and rifampin
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How is XDR-TB defined?
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Resistance to at least isoniazid and rifampin plus
Resistance to fluoroquinolones and 1 of the second line injectable drugs = amikacin, kanamycin, capreomycin |
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Time line for TB diagnosis
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Symptom duration > 2 weeks
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How do primary and reactivation disease differ in location?
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Reactivation: upper
Primary: lower |
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How do children differ from adults in diagnosis?
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Children have less bacilli, might have a false negative
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How are sputum samples collected for TB diagnosis?
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3 samples on 3 separate days
Every 8 hours, with 1 specimen in early morning |
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What stain is better than acid fast for TB?
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Auramine
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Which requires more organisms: culture or smear?
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Culture
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When can a DNA probe be used in TB?
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Once there is growth in culture
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What is MODS?
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Microscopic observation drug susceptibility
Broth cultures are examined microscopically to detect growth and cord formation |
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How is MDR-TB diagnosed in resource poor settings?
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Line probe assay
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INH MOA
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Product activated by catalase-peroxidase hemoprotein (KatG). Inhibits InhA, a NADH carrier protein reductase involved in fatty acid synthesis
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How does resistance to INH develop?
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Mutations in target gene (InhA) and activating enzyme (KatG)
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What is the toxicity of INH?
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Hepatits, peripheral neuropathy
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Rifampin MOA.
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Inhibits essential rpoB gene product, the beta-subunit of DNA-dependent RNA polymerase. Binds to the beta-subunit, blocking transit of growing RNA chain early in txn.
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What is the toxicity of rifampin?
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Hepatits, orange body fluids, flu like syndrome
Several drug interactions due to induction of hepatic microsomal enzymes. Lowers levels of warfarin, oral contraceptives, HIV-1 protease inhibitors. |
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Pyrazinamide MOA:
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Poorly understood. Inhibits various functions of M. TB.
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Toxicity of pyrazinamide.
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Hepatits, arthralgia, hyperuricemia, gout, rash
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Ethambutol MOA:
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Inhibits arabinosyl transferases involved in cell-wall biosynthesis
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Toxicity of ethambutol
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Retrobulbar neuritis (visual acuity, red-green color discrimination) peripheral neuropathy, rash
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What is the weakest drug?
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Ethambutol
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What TB populations are INH, PZA, and RIF most active against?
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INH: rapidly multiplying (caseum)
PZA: slowly multiplying (acidic) RIF: sporadically multiplying |
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Define early bactericidal activity (EBA).
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Decrease in colony counts in first 2 days of treatment
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Define sterilizing activity.
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Killing of slowly multiplying organisms (acidic environment) and sporadically multiplying organisms. Assessed by negative sputum cultures after 2 months.
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What drug has the best EBA?
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Isoniazid
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What is the spectrum of TB drugs in sterilizing activity?
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Rifampin
Pyrazinamide Streptomycin Isoniazid |
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What is the current TB treatment?
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INH/rifampin/pyrazinamide/ethambutol x 2 months plus INH/rifampin x 4 months (total 6 months)
Treatment duration: 6 months for most pulmonary and extrapulmonary disease Extent to 9 months if cavity on initial chest radiography and culture + after 2 months of treatment |
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What is the recommended treatment for MDR-TB?
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4-6 drugs
Include injectable agent + fluoroquinolone Treat 18-24 months |
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Fluoroquinolones: MOA?
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DNA gyrase inhibitor
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Diarylquinolone: MOA?
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ATP synthase inhibitor
(same as TMC drug) |
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OPC-67683 family
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Nitroimidazole
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PA-824 activity
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Nitroimidazole
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What is the typical therapy for latent TB?
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9 months of INH
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