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Medicine > (ID)- Tuberculosis > Flashcards

(ID)- Tuberculosis Flashcards

1
Q

What causes TB?

A

Mycobacterium tuberculosis

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2
Q

What type of bacteria is mycobacterium tuberculosis?

A

Aerobic acid-fast bacilli

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3
Q

What staining is required for TB and why?

A

Zeihl-Neelsen stain

Waxy coating
Resistant to acids

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4
Q

What is the disease course of TB?

A

Immediate clearance
Most cases
Primary active TB
Active infection after exposure
Latent TB
Bacteria are present but not symptomatic or contagious
Secondary TB
Reactivation of latent TB

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5
Q

What is miliary TB?

A

Immune system unable to control infection

Disseminated and severe disease develops

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6
Q

What are the symptoms of active TB?

A

Non-resolving cough
Unexplained persistent fever (low or high grade)
Drenching night sweats
Weight loss

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7
Q

What is the histology for TB?

A

Caseating granulomatous inflammation

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8
Q

When is latent TB present?

A

Immune system encapsulates bacteria and stops progression of disease

Most patients never develop active infection

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9
Q

What is secondary TB?

A

When latent TB reactivates and infection develops due to immunosuppression

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10
Q

Where is the most common site for TB infection?

A

Lung apices to get plenty of oxygen

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11
Q

What is extrapulmonary TB?

A

TB in other areas e.g.
- Lymph nodes
- Pleura
- CNS
- Pericardium
- GI
- GU
- Bones and joints
- Skin

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12
Q

What is a cold abscess?

A

Firm, painless abscess caused by TB in the neck

No inflammation, redness or pain

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13
Q

What are the risk factors of TB?

A
  • Close contact with active TB (household member)
  • Immigrants from high TB prevalence
  • People with relatives or close contacts from countries with a high rate of TB
  • Immunocompromised
  • Malnutrition, homelessness, drug users, smokers and alcoholics
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14
Q

What is the BCG vaccine?

A

Bacillus Calmette-Guérin vaccine

Intradermal injection of live attenuated Mycobacterium bovis

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15
Q

Why can Mycobacterium bovis be used for vaccination?

A

Close relative of Mycobacterium tuberculosis

Does not cause diseases in humans

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16
Q

What does the BCG vaccine protect against?

A

Severe and complicated TB

Less against pulmonary TB

17
Q

Before vaccination what test is used on patients?

A

Mantoux test

Vaccine only given if negative

18
Q

What are patients assessed for before giving the BCG vaccine?

A

Immunosuppression
HIV

Due to risk of live vaccine

19
Q

Who is offered a BCG vaccine?

A

Healthcare workers
Patients at increased risk of TB

20
Q

How does TB present?

A

Chronic, gradually worsening symptoms

Most cases with pulmonary disease with systemic symptoms
- Cough
- Haemoptysis
- Lethargy
- Fever or night sweats
- Weight loss
- Lymphadenopathy
- Erythema nodosum
- Spinal pain in spinal tuberculosis (Pott’s disease of the spine)

21
Q

What investigations are used for TB?

A

Ziehl-Neelsen stain

Immune response tests
- Mantoux test
- Interferon-gamma release assay (IGRA)

Suspected disease to support diagnosis
- CXR (mediastinal lymphadenopathy or cavitating pneumonia)
- CT (lymphadenopathy
- MRI (can show leptomeningeal enhancement in TB meningitis)

22
Q

What is the mantoux test?

A

Injecting tuberculin into the intradermal space on the forearm

Infection creates a bleb under the skin

After 72 hours skin injection site is looked at, induration of 5mm or more is positive

23
Q

What is tuberculin?

A

Collection of tuberculosis proteins isolated from bacteria

24
Q

What is the interferon-gamma release assay?

A

Blood sample mixed with antigens from mycobacterium tuberculosis

After previous contact with mycobacterium tuberculosis WBCs become sensitised to bacterial antigens and will release interferon-gamma on contact

Positive result is if interfon-gamma is released

Does not differentiate between active and Latent TB

25
Q

What does primary tuberculosis show on CXR?

A

Patchy consolidation
Pleural effusions
Hilar lymphadenopathy

26
Q

What does secondary TB show on CXR?

A

Patchy or nodular consolidation
Cavitation (gas-filled spaces)

Typically in upper zones

27
Q

What does disseminated miliary TB show on CXR?

A

Millet seed appearance uniformly distributed across lung fields

28
Q

When are culture samples taken?

A

Before starting treatment

Allows testing for drug resistance

Cultures can take several months

29
Q

How are cultures taken for TB?

A

Sputum cultures (3 separate sputum samples collected)
Mycobacterium blood cultures
Lymph node aspiration or biopsy

30
Q

What is done if the patient cannot produce enough sputum for the sample?

A

Sputum induction with nebulised hypertonic saline

Bronchoscopy and bronchoalveolar lavage

31
Q

When is nucleic acid amplification tests used for TB?

A

Diagnosing TB in patients with HIV or under 16
Risk factors for multidrug resistance

32
Q

How is latent TB treated?

A

Isoniazid and rifampicin for 3 months
or
Isoniazid for 6 months

33
Q

How is active TB treated?

A

Rifampicin 6 months
Isoniazid 6 months
Pyrazinamide 2 months
Ethambutol 2 months

34
Q

Why is Vitamin B6 (pyridoxine) prescribed alongside when treating active TB?

A

Isoniazid causes peripheral neuropathy and B6 is given to help prevent this

35
Q

What other management must be done when treating TB?

A
  • Testing for other infectious diseases (HIV, HepB,C)
  • Contact testing
  • Notifying UKHSA of suspected cases
  • Isolating patients with active TB to prevent spread (2 weeks at least)
  • Individualised regimes for MDR TB and extrapulmonary disease
  • Negative pressure rooms (ventilation systems remove air to prevent it spreading to ward)
36
Q

What are the side effects of treating TB?

A

Rifampicin
Red urine and tears
Potent inducer of P450 enzymes, reduces effect of COCP

Isoniazid (I’m-so-numb-azid)
Peripheral neuropathy, pyridoxine (B6) prescribed alongside

Pyrazinamide
Hyperuricaemia, gout and kidney stones

Ethambutol
Colour blindness and reduced visual activity

Rifampicin, Isoniazid and Pyrazinamide all associated with hepatotoxicity
Do LFTs before giving

Medicine (111 decks)

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