Lecture 1 Flashcards

1
Q

What tests are you required to do if you enter the UK for, a country with common TB infections ?

A

Sputum test and x-ray

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2
Q

Define latent

A

You are infected with the bacteria but do not have the signs or symptoms

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3
Q

What patients are at more risk if they develop TB?

A

HIV patients

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4
Q

What are the symptoms of TB?

A

More than 3 weeks cough that is getting worse persistent and productive, temperature,fever, night sweats and chills - occurring at different times of the day, unexplained weight loss and coughing up blood

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5
Q

How do we diagnose TB?

A

X-rays, clinical examination, PCR test (rapid within 2 hrs)

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6
Q

How do we diagnose latent TB?

A

Tuberculin Skin Test (Mantoux test), molecular tests (interferon gamma release assay)

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7
Q

What is the tuberculin skin test ?

A

Tuberculin injected sc into forearm possible if skin lesion >10 mm diameter post 48-72 hrs

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8
Q

Describe stage 1 of TB

A

Inhaled in droplets, settle in alveoli of the lung, start to grow, stimulates an immune response and macrophages come out,they are phagocytosed by macrophages but they do not kill the bacilli

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9
Q

Describe stage 2 of TB

A

Asymptomatic/ mild fever, body isn’t effective at removing TB, bacteria multiple in size, macrophages in lungs 7-21 days, macrophages burst and incoming macrophages phagocytose release M.TB and the cycle repeats. This continues for 3-4 weeks

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10
Q

Describe stage 3 of TB

A

At 6 weeks symptoms of disease start to appear, cell mediated response initiated (T cell, B cell, fibroblasts), collagen fibres form around affected sites, granulomas (tubercules) formed in lung

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11
Q

Describe stage 4 of TB

A

Bacteria multiply inside macrophage, granuloma burst - uncontrolled lysis. Bacteria spread - new sites of infection process repeats. Enzymes released - destroys local tissues causing lesions

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12
Q

What is disseminated TB?

A

Spreads throughout body and can infect multiple organs

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13
Q

Name the 1st line treatments for active TB

A

Combination of 4 drugs over 6-9 months
Rifampicin and isoniazid - 6-9 months
Pyrazinamide and ethambutol for the first 2 months

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14
Q

Name the 1st line treatment for latent TB

A

Isoniazid 6 months or Rifampicin and isoniazid for 3 months

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15
Q

Describe the MoA of Rifampicin

A

Bactericidal to all metabolising cells
Targets mRNA production
Inhibits RNA polymerase
Oral
Absorption affected by food

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16
Q

What are the side effects of Rifampicin?

A

Liver damage, hypersensitivity, increased activity of other drugs eg.contraceptive pill. Red colour in body fluids e.g. urine

17
Q

Define the MoA of isoniazid

A

TB specific
Synthesis of mycolic acid
Pro drug
Oral
Bactericidal to active growing bacilli
Bacteriostatic to very slow growing bacilli
Metabolised in the liver, excreted in the kidneys

18
Q

Side effects of isoniazid

A

Hypersensitivity, peripheral neuropathy, liver toxicity, increased efficacy of hormonal birth control

19
Q

Define MoA for pyrazinamide

A

Pro drug
Bactericidal to dormant bacilli
Precise mechanism/action is unclear
Oral

20
Q

Side effects of pyrazinamide

A

Joint pain, liver damage and hypersensitivity

21
Q

Define MoA of ethambutol

A

Bacteriostatic against growing bacilli
Increased permeability by affecting synthesis of arabinogalactan in cell wall
Oral
50% excreted unchanged in the urine

22
Q

Side effects of ethambutol

A

Nerve neuritis and joint pain

23
Q

How is TB prevented ?

A

Immunisation, BCG vaccine (live attenuated) given to high risk groups such as areas with high incidence, HIV positive, children with parents from a high risk country

24
Q

Why is it difficult to treat TB?

A

Thick cell wall - antibiotics need to penetrate layer of mycolic acid
Intracellular - antibiotics need to get inside the macrophage
Long periods of treatment - side effects
Slow growing aren’t metabolically active

25
Q

Define MDR-TB

A

Strains resistant to at least the 1st line drugs Rifampicin and isoniazid

26
Q

Define pre XDR

A

Strains resistant to more than two 1st line drugs rifampicin and isoniazid aid resistant to any group A fluroquinolones

27
Q

Define XDR-TB

A

Strains resistant to more than more two 1st line drugs rifampicin and isoniazid and also resistant to any group A fluroquinolones and also at least one additional group A drug

28
Q

What shaped bacteria is TB

A

Rod shaped bacteria

29
Q

What is the doubling time of TB?

A

15-24 hours

30
Q

When TB becomes infected in the lungs what is it known as?

A

Pulmonary TB

31
Q

When TB spreads to other organs what is it known as?

A

Extrapulmonary

32
Q

What is the TB cell wall rich in?

A

Lipids, lipoarbinomanan, arabinoglactan , mycolic acid, => thick waxy lipid cell wall

33
Q

What is the TB cell wall resistant to?

A

It is very hydrophobic
Resistant to drying, weak disinfectants, some antibiotics

34
Q

Describe process of the PCR test for active TB

A

Someone spits into a cartilage, and it gets led into a machine
Rapid (within 2 hrs)
Sensitive to low levels of bacteria
Can detect rifampicin resistance
Can detect isoniazid resistance