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III > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

What is tuberculosis?

A

Caused by mycobacterium tuberculosis which is a slow growing acid fast bacterium.

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2
Q

What is the structure of mycobacterium tuberculosis?

A

Acid fast:

Cell wall rich in lipids, v. hydrophobic, resistant to drying and weak disinfectants.

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3
Q

What is the first stage in the primary progression of TB?

A

Bacili inhaled in droplets, phagocytosed by macrophages.

The macrophages do not destroy the bacili.

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4
Q

What is the second stage in the progression of TB?

A

The M.TB now in the macrophages multiplies for 7-21 days before the macrophage burts open. The incoming macrophages then phagocytose the released M.TB.

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5
Q

What is the third stage in the progression of TB?

A

Cell mediated immune response is initiated and tubercules are formed.

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6
Q

What is the fourth stage of the progression of TB?

A

Multiplication of M.TB inside macrophages continues until uncontrolled lysis occurs.

Enzymes are thus released that destroy local tissue causing the formation of lesions.

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7
Q

What are the signs and symptoms indicative of TB infection?

A

Cough, afternoon fever, weight loss, blood stained sputum, night sweats.

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8
Q

How is active TB diagnosed?

A

Chest X ray: white lesions replace alveoli with scar tissue.

Sputum test: smears and/or cultures: visualise TB in sputum via microscopy and staining.

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9
Q

How is latent TB diagnosed?

A

Tuberculin skin test, if lesion forms > 10mm diameter after 48-72hr.
Molecular assay:
- Xpert MTB/RIF assay
- IFNgamma tests

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10
Q

How can TB be prevented?

A

Immunisation: BCG vaccine given to high risk groups.

New vaccines in clinical trials.

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11
Q

What are the main criteria for anti-TB drugs?

A
  1. Active intracellular, as TB infects cells.
  2. Combination therapy conducive: interaction with other anti-TB drugs must be at a minimum
  3. Ability to treat distinct TB populations.
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12
Q

What are the 4 first line drugs used as anti-TB drugs?

A

Rifampicin
Isoniazid
Pyrazinamide
Ethambutol

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13
Q

What are the effects of Rifampicin use?

A

Inhibits RNA synthase.
Decreased absorption via food, can cause liver damage, hypersensitivity, decreased actions of other drugs and red coloured bodily fluids.
Bactericidal

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14
Q

How does Isoniazid work?

A

Decreases the synthesis of mycolic acids.
Decreases efficacy of hormonal birth control.
Prodrug
bactericidal or static

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15
Q

How does pyrazinamide function as an anti-TB drug?

A

Bactericidal pro-drug that deceases the synthesis of mycolic acid and damages the TB bacterial membrane.
Bactericidal

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16
Q

Ethambutol

A

First line anti-TB alongside: Rifampicin, isoniazid and pyrazinamide.

17
Q

How does ethambutol function against TB?

A

Increases the permeability of the cell wall.
Bacteriostatic
Optic neuritis which is reversible.

18
Q

Which anti-TB drug decreases efficacy of hormonal contraceptive?

A

Isoniazid
Decreases the synthesis of mycolic acids.
Decreases efficacy of hormonal birth control.
Prodrug

19
Q

Rifampicin

A

First line anti-TB alongside: Ethambutol, isoniazid and pyrazinamide.

20
Q

Which of the 4 first line anti-TB drugs are bactericidal only?

A

Rifampicin.
Isoniazid (can be both)
Pyrazinamide.

Ethambutol is only bacteriostatic.

21
Q

What are the second-line anti-TB drugs?

A 
Streptomycin: aminoglycoside 
Capreomycin: aminoglycoside 
Cycloserine: neurological side effects
Ciprofloxacin: Quinolone drug
Azithromycin: newer macrolide.
22
Q

Which anti-TB drug colours bodily fluids red?

A

rifampicin:
Inhibits RNA synthase.
Decreased absorption via food, can cause liver damage, hypersensitivity, decreased actions of other drugs and red coloured bodily fluids.

23
Q

Cycloserine

A

2nd line antiTB

Can cause neurological side effects,

24
Q

What is the treatment for standard TB? (Short-course)

A

Isoniazid + Rifampicin + Pyrazinamide + ethambutol for two months.

THEN: Isoniazid and Rifampicin alone for a further 4 months.

25
Q

Streptomycin

A

2nd line anti-TB.

Aminoglycoside.

26
Q

Why would pyridoxal phosphate be included in TB therapy?

A

To obviate peripheral neuropathy caused by isoniazid)

27
Q

Azithromycin

A

2nd line antiTB
Never macrolide
50s subunit

28
Q

For latent TB, what is the treatment?

A

6-9 months of daily Isoniazid alone
OR
three months of weekly (12 doses total) of Isoniazid/rifapentine combination.

29
Q

How does TB resistance develop and what strains are resistant?

A

Poorly managed TB care.
MDR-TB: strains resistant to >2 first line drugs
XDR-TB: strains resistant to >2 first line drugs and >3 of 6 second line drugs.
XXDR-TB and DR-TB not recognised by WHO but believed to exist.

30
Q

What is MDR-TB?

A

Strains resistant to >2 first line drugs.

31
Q

What is XDR-TB?

A

Strains resistant to >2 first line drugs AND >3 of 6 second line drugs.

III (24 decks)

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