pharm ID; anti TB

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  1. how is TB transmitted?
    • Airborne disease caused by the bacterium Mycobacterium tuberculosis (M. tb)
    • M. tb complex (M. tb, M. bovis, M. africanum, M. microti, M. canetti,  M. caprae, M. pinnipedii, and M. mungi) can cause TB disease
    • Majority of TB cases caused by M. tbo  
    • M. tb organisms also called tubercle bacilli
    • M. tb spread via airborneparticles called droplet nuclei
    • Expelled when person with infectious TB coughs, sneezes, shouts, or sings
    • Transmission occurs when droplet nuclei inhaled and reach the alveoli of the lungs, via nasal passages, respiratory tract, and bronchi
  2. what is a latent TB infection?
    • Granulomas may persist (LTBI), or may break down to produce TB disease
    • 2 to 8 weeks after infection, LTBI can be detected via TST or interferon-gamma release assay (IGRA)
    • The immune system is usually able to stop the multiplication of bacilli
    • Persons with LTBI are not infectious and do not spread organisms to others
  3. TB disease
    • In some, the granulomas break down, bacilli escape and multiply, resulting in TB disease
    • Can occur soon after infection, or years later
    • Persons with TB disease are usually infectious and can spread bacteria to others
    • Positive M. tb culture confirms TB diagnosis
  4. sites of TB dz:
    • Lungs (pulmonary): most common site; usually infectious
    • Miliary: occurs when bacilli spread to all parts of the body; rare, but fatal if untreated
    • Central nervous system: usually occurs as meningitis, but can occur in brain or spine
    • Outside the lungs (extrapulmonary): usually not infectious, unless person has
    • Concomitant pulmonary disease,
    • Extrapulmonary disease in the oral cavity or larynx, or
    • Extrapulmonary disease with open site, especially with aerosolized fluid.
  5. what is the risk of developing TB dz with normal immune system?
    • Untreated, 5% of infected persons with normal immunity develop TB in first 1–2 years post infection, another 5% later in life
    • Thus, about 10% of infected persons with normal immunity will develop TB at some point in life if not treated
  6. what is the risk of developing TB dz with weak immune system?
    • Untreated, 5% of infected persons with normal immunity develop TB in first 1–2 years post infection, another 5% later in life
    • Thus, about 10% of infected persons with normal immunity will develop TB at some point in life if not treated
  7. discuss treatment regarding LTBI vs disease:
    • Person with LTBI (infected): Should consider treatment for LTBI to prevent TB disease
    • Person with TB disease (infectious): Needs treatment for TB disease
  8. drug-resistant TB-
    caused by:
    delay in  detecting:
    • Caused by organisms resistant to one or more TB drugs
    • Transmitted same way as drug-susceptible TB, and no more infectious
    • Delay in detecting drug resistance may prolong period of infectiousness because of delay in starting correct treatment
  9. what are multidrug-resistant (MDR) drugs?
    MDR TB caused by bacteria resistant to best TB drugs, isoniazid and rifampin
  10. what is extensively drug-resistant (XDR) TB?
    XDR TB caused by organisms resistant to isoniazid and rifampin, plus fluoroquinolones and ≥1 of the 3 injectable second-line drugs
  11. what are 2 ways drug resistance develops?
    • Primary resistance develops in persons initially infected with resistant organisms·    
    • Secondary (acquired) resistance develops during TB therapy
  12. who are the candidates for tx of LTBI?
    • HIV-infected persons
    • Recent contacts of persons c/ infectious TB
    • Persons with fibrotic changes on chest x-ray
    • People who are immunosuppressed
    • Recent arrival from another country
    • Injection drug users
  13. inhalation of mycobacterium tuberculosis can lead to:
    overt disease or may cause a latent infection.
  14. People with latent infections have the bacterium but are:
    Latent infection may develop into:
    • asmptomatic
    • an active infection, particularly in the immunosupressed
  15. mycobacteria produce:
    what compromises approx. 60% of the cell wall?
    what type of envelope?
    their abundant lipid prevents:
    • envelopes rich in fatty acids & lipids
    • Mycolic acid, one type of fatty acid
    • have a gram + cell envelope
    • prevents penetration of   the Gram stain so they are not able   to be characterized with this method
  16. why does treatment of mycobacterial infections require multiple drugs for extended periods of time?
    • Difficult to eradicate
    • Caused by slowly dividing bacteria that   progressively weaken the body
    • Antibiotics tend not to work as well against   slowly dividing bacteria.
    • Thus mycobacteria are more likely to be    resistant to antibiotic treatments.
  17. Antimicrobial Agents for Mycobacterium Tuberculosis Infections-
    Active dz:
    latent infection:
    • Active: (Isoniazid + Rifampin + Pyrazinamide + Ethambutol ) X 2 months;
    • followed by (Isoniazid + Rifampin*) X 4 months

    latent: isoniazid x 9 months
  18. If the infecting strain is resistant to rifampin and  isoniazid, Treatment of MDR requires using:
    • requires using second-line drugs,   which tend to be less effective or more toxic
    • Second line drugs include streptomycin, amikacin, cycloserine, a quinolone, ethionamide, capreomycin or p-aminosalicylic acid.  
    • At least three previously unused drugs to which the   mycobacterium is susceptible to in vitro should  be used for a minimum of eighteen months.
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pharm ID; anti TB
2013-06-23 01:36:05

antimycobacterials. Overview
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