PBL 6 - Tuberculosis Flashcards

1
Q

How does tuberculosis normally spread? (1 mark)

A

Mainly by inhalation of infected airborne aerosol (air containing water droplets containing m.
tuberculosis). (

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2
Q

Which organs are normally first infected by tuberculosis, and why is this? (1 mark)

A
The lungs (1/2 mark). M.tuberculosis prefers a high level of oxygen to grow and the lungs provide
this (1/2 mark)
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3
Q

Explain carefully why tuberculosis is difficult to treat with drugs (1 mark)

A

M. tuberculosis is intracellular (1/2 mark) and has a waxy cell wall that resists penetration by drugs
(1/2 mark). Antibiotics have to penetrate both the host mammalian cell and the bacterial cell wall to
be effective .

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4
Q

What is usually the first symptom of pulmonary tuberculosis? (1 mark). List four other
signs/symptoms that may present. (2 marks)

A

First symptom: Productive cough (1 mark)
Other symptoms: Night sweats, Weight loss, Loss of appetite, Haemoptysis, (coughing up blood)
Chronic fatigue, (Any four 1/2 mark each)

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5
Q

Give four separate methods used for the diagnosis of tuberculosis (2 marks)

A

Four from : PCR (polymerase chain reaction) (from sputum) Skin test (Mantoux/Pirquet) Chest Xray
Histological examination of biopsy Microbiological culture (sputum) Any four (1/2 mark each)

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6
Q

What four drugs make up the normal first line treatment protocol for tuberculosis? (2 marks)

A

Rifampicin, Isoniazid, Pyrazinamide, ethambutol (1/2 each) (RIPE)

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7
Q

What parts of the body can TB also infect? (2)

A

lymph
nodes, bones and joints, kidneys, brain, gut, the skin
(extra-pulmonary and non infectious)

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8
Q

Why are mycobacteria named acid-fast bacilli? (1)

A

resistance to decoloration with acid washing;

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9
Q

How long does it usually take to culture mycobacteria? (1)

A

2-6 weeks

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10
Q

What is the pathophysiology of TB? (3)

A

o Primary infection – engulfed by macrophages, forms granulomas – asymptomatic
o Latent infection – bacteria dormant for months-years
o Secondary infection – reactivation of bacteria, usually in lung apex causing symptoms e.g immunosuppressed (APEX as most oxygenated)

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11
Q

What percentage of the population have TB? (1)

A

1/3rd of population

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12
Q

How do you do the Mantoux skin test? (2)

A

Inject Tuberculin intradermally, measure cell mediated response
 5mm pos in – HIV positive, old healed TB, recent TB contact
 10mm pos in – Injection drug users, high risk setting, recent arrivals
 15mm pos in – No TB risk factors

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13
Q

What is the BCG vaccine? Why might this give a false positive on mantoux test? (2)

A

Vaccine prevent against TB

antibodies to TB still present.

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14
Q

What are features of a chest X-ray you would see in someone with TB? (2)

A

Apical consolidation, bilateral opacities/calcification/cavitation
Hilar shadowing

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15
Q

What would you detect in a sputum test? (1)

A

Detect bacteria

or fungi

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16
Q

Why would you take a histological examination of biopsy specimens in TB (2)

A

Multinucleate Langerhans giant cells, AFBs inside macrophages
takes a long time for microbiology
In extra-pulmonary TB - Culture can be negative

17
Q

Risk factors for TB (2)

A
Close contact
Ethnic minorities
Alcoholics
HIV positive
Young and elderly 
Homeless
18
Q

What drug must you not take if you are taking rifampicin? (1)

A

Oral contraceptives

as acts on liver, may not work

19
Q

What are possible side effects of the TB treatment (3)

A

Rifampicin = Liver enzymes, orange secretions, hepatotoxicity in pregnancy
Isoniazid = Peripheral neuropathy, hepatotoxic
Ethambutol = Optic neuritis leading to red-green colour blindness
(Liver problems, vision changes, neuropathy)

20
Q

What is MDR-TB? (2)

A

Multi-drug resistant TB

  • Resistant to isoniazid and rifampicin- MDR-TB
  • Must take streptomycin, amikacin, levofloxacin
21
Q

What is the relationship between TB and HIV? (2)

A

TB and HIV infection act synergistically, each
condition exacerbating the other
Reactivation is higher if you have TB

22
Q

How is TB prevented in the UK (3)

A

o Contact tracing and screening
= Detect source of infection, vaccinate, offer mantoux test to people close to those with TB
BCG Vaccine – given to schoolchildren at around 12/13 years of age + High risk groups
Identifying and treating all those with TB

23
Q

What is CCDC? (1)

A

Consultant in Communicable Disease Control

24
Q

What is Sputum

A

Sputum is a thick fluid produced in the lungs and in

the adjacent airways

25
Q

What is miliary TB

A

When the body fails to control the initial infection which invades the blood stream

26
Q

What stain do you use in mycobacteria tuberculosis

A

Ziehl-Neelson (red)

Auramine (orange)

27
Q

MoA rifampicin

A

RNA polymerase inhibitor

6months

28
Q

MoA Isoniazid

A

Inhibits mycoloic acids in cell wall

6 months

29
Q

MoA pyrazinamide

A

Inhibits FA synthesis,

2 months

30
Q

MoA ethambutol

A

Inhibits cell wall synthesis

31
Q

What would you take in multi-drug resistant TB

A

Streptomycin
Amikacin
Levofloxacin
(instead of rifampicin or isoniazid)

32
Q

How long do you need to incubate bacteria

A

2-8 wks

33
Q

How much tuberculin in mantoux test

A

0.1 ml of 5 tuberculin units

34
Q

What is tuberculin

A

o purified protein derivative (PPD) extracts of

Mycobacterium tuberculosis, M. bovis, or M. avium th

35
Q

Which drug is not given to children

A

Ethambutol