Tuberculosis Flashcards

1
Q

Describe the epidemiology of TB

A

30% of the world’s population have latent TB

2 billion deaths from TB each year

Highest incidence in central and southern africa

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2
Q

Describe the aetiology of TB

A

Caused by mycobacterium tuberculosis

Gram stain -ve but similar structure to gram stain +ve.

Unique impermeable cell wall

Transmission predominantly from aerosolised droplets or fomites.

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3
Q

Where is latent TB often contained in the body?

A

Hilar lymph nodes and Ghon focus

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4
Q

Describe the histopathology of TB

A

Granulomatous inflammation with caseous necrosis

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5
Q

List the host risk factors for TB

A

Extremes of age

Stress and starvation

Immunocompromised host:

  • HIV
  • Alcoholism
  • Steroids and immunosuppressants
  • Anti TNF treatment for autoimmune diseases

Other risk factors:

  • Malignancy
  • Renal failure
  • Diabetes mellitus
  • Vitamin D deficiency
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6
Q

Name some clinical features of TB

A

Varies according to site of infection; insidious onset.

Systemic features:

  • Fevers
  • Night sweats
  • Weight loss

Pulmonary:

  • Cough
  • Sputum
  • Haemoptysis
  • Dyspnoea

Lymph nodes = typically cervical & axillary (may become necrotic)

Other sites = local symptoms of inflammation & tissue necrosis

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7
Q

List investigations for TB

A
  • Full blood count (FBC) : possible leukocytosis (↑ WCC)
  • Urea & electrolytes (U&Es) : usually normal
  • Liver function tests (LFTs) : possibly raised
  • C-reactive protein (CRP) : mild-moderate rise only
  • Lactate : usually normal (no sepsis)
  • Chest radiograph (CXR) : upper lobe cavitating pneumonia
    • Miliary shadowing
    • Hilar lymphadenopathy
    • Pleural effusion
    • Pericardial effusion

CT/MR scans : thorax / abdomen / spine / bones / head

Laparoscopy / Thoracoscopy : direct visualisation & biopsy

Other biopsies : lymph nodes / bones / cold abscesses

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8
Q

What does this x-ray show?

A

Left upper lobe tuberculosis

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9
Q

What does this x-ray show?

A

Miliary TB (TB infection was never contained in ghon focus, spread throughout body tissues)

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10
Q

What does this x-ray show?

A

Pericardial effusion caused by TB.

Large due to slow growing TB

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11
Q

Which microbiological investigations can be conducted to confirm TB?

A

Sputum:

  • Ziehl-Neelsen stain → Acid-Fast Bacilli (AFBs) = pink
  • Auramine-Phenol stain → AFBs = fluorescent

Sputum, pleural fluid, pericardial fluid, blood, urine, CSF & biopsies→ culture (on Löwenstein–Jensen or liquid medium) & sensitivities

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12
Q

How is TB treated?

A

Multi-drug treatment required to prevent resistance

  • Rifampicin for 6 months
  • Isoniazid for 6 months
  • Pyrazinamide for 2 months
  • Ethambutol for 2 months

(TB in the CNS requires 12 months of treatment)

Pyridoxine to prevent neuropathy from isoniazid

Steroids if CNS or pericardial infection

Vitamin D if deficient

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13
Q

What can be given to prevent TB?

A

Prevention of primary infection :

For active TB cases :

  • Respiratory isolation
  • Prompt diagnosis & treatment
  • Contact tracing & testing

Vaccination with Bacillus Calmette–Guérin (BCG) :

  • ~25% prevention of primary infection
  • ~70% prevention of active infection
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14
Q

How is latent TB screened for?

What is the treatment of latent TB?

A

Prevention of re-activation :

  • Screening for latent TB infection & treatment :
    • Tuberculin skins tests (TST)
    • TB interferon-gamma release assays (IGRA)

Treatment for latent TB :

  • Rifampicin & isoniazid for 3 months
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