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RESP. MICROBIOLOGY > L6 Pathogenesis, Resistance, & Transmission of TB > Flashcards

L6 Pathogenesis, Resistance, & Transmission of TB Flashcards

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Biology 101 flashcards
1
Q

What are the most common symptoms of TB ?

A
  1. Hemoptysis
  2. B symptoms
    - fever
    - weight loss
    - drenching night sweats
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2
Q

What are the M. Tuberculosis complex ? What are the members ?

A

It causes TB

Members are :

  1. M. tuberculosis
  2. M. bovis
  3. M. africanum
  4. M. canettii
  5. M. microti.
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3
Q

What is the structure of Cell wall of M. tuberculosis ?

A
  1. Mycolic acid :
    - complex hydroxylated ( branched chain fatty acid ) with increases carbon number
  2. Glycolipids :
    - responsible of ( the cord formation bacteria ) clump like serpents in liquid medium
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4
Q

Why M. Tuberculosis when stained appears as Gram-positive ?

A

Mycolic acid causes resistance to de-staining by acid-alcohol after being stained by aniline dyes

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5
Q

What is the shape of M. Tuberculosis after staining with Acid fast stain ?

A

Pink-staining bacilli

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6
Q

What are the types of media for M. Tuberculosis?

A
  1. SOLID ( egg-based medium )
    * Lowenstein-Jensen (LJ) medium
    * agar-based medium
    * Middlebrook 7H10 agar
    Require 3-4 weeks to see growth
  2. LIQUID ( BACTEC )
    Takes 2 weeks to see the growth
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7
Q

What are the shape of The colonies on Lowenstein-Jensen medium ?

A

Brown granular colonies

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8
Q

What are the outcomes of exposure to MTB ?

A
  • Immediate clearance of organism
  • Rapidly progressive active disease (primary disease)
  • Latent infection
  • Active disease many years after infection (reactivation disease)
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9
Q

What are the site of primary lung tuberculosis ?

A

lower part of upper lobe or upper part of lower lobe as it is obligate aerobic and these area have high oxygen tension

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10
Q

What is the mechanism of primary TB ?

A
  • Inhaled bacilli implant in lower part of upper lobe or upper part of lower lobe
  • Engulfed by alveolar macrophages in which they multiply causing inflammation and consolidation (Ghon focus)
  • Spread of bacilli to regional lymph nodes … Ghon complex or primary complex
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11
Q

What are the cells that you can find in granuloma ?

A
  1. Epitheloid cells ( activated microphages )
  2. Giant cells
  3. T cells
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12
Q

What is the cause of the induration in mountoux tuberculin test ?

A

Tissue Infiltration by :

  1. Lymphocytes
  2. Mononuclear macrophages
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13
Q

How can miliary TB spread ?

A
  1. By blood
  2. By lymphatics
  3. By direct spread through swallowing saliva
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14
Q

Where you can find the lesion in primary and secondary TB ?

A

In primary : upper part of lower lobe or lower part of upper lobe

In secondary : apical sites of the lung

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15
Q

What are the virulent factors of MTB ?

A
  1. Mycolic acid glycolipids + trehalose dimycolate&raquo_space;> granuloma formation
  2. Lipoarabinomannan (LAM)&raquo_space;> produce cytokines that will inhibit oxidative stress
  3. Sulfatides&raquo_space;> released from the phagosome to inhibit phagosome-lysosome fusion
  4. Cell wall&raquo_space;> prevent degradation by lysosome if the fusion occur
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16
Q

What are the first and second line treatment of TB ?

A
  1. First line :
    Sterilizing > rifampicin and pyranizamide
    Bactericidal > isonazide and streptomycin and ethambutol
  2. Second line:
    * polypeptides
    * floroquinlones
    * amino-glycoside
    * cycloserine
    * thionamides
17
Q

What is most widely used regimen ?

A
  1. initial intensive phase of rifampicin, isoniazid, pyrazinamide and ethambutol for 2 months
  2. rifampicin and isoniazid for 6 months.
18
Q

What are the types of drug resistance of TB ?

A
  1. Mono-resistant TB: Resistant to anyone first-line drug
  2. Poly-resistant TB: Resistant to at least any 2 first-line drugs (but not both isoniazid and rifampin)
  3. Multi-drug resistant TB (MDR-TB): Resistant to at least isoniazid + rifampin, possibly additional chemotherapeutic agents.
  4. Extensively drug resistant TB (XDRTB): Resistant to
    * isoniazid + rifampin
    * at least one of three injectable second-line drugs (capreomycin, kanamycin, amikacin)
    * a fluoroquinolone.
19
Q

What are the organs that are affected in M. Bovis ?

A
  1. Intestine
  2. Mesenteric lymph node
  3. Cervical lymph node&raquo_space; scrofula
  4. Tonsils
20
Q

What is scrofula ?

A

It is cervical tuberculosis lymphadenopathy

RESP. MICROBIOLOGY (3 decks)

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