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(LUSUMA) Respiratory System > S9) Tuberculosis > Flashcards

S9) Tuberculosis Flashcards

1
Q

What is tuberculosis?

A

Tuberculosis is a bacterial infection caused by Mycobacterium tuberculosis which mainly affects the lungs, but can affect any part of the body (abdomen, glands, bones and nervous system)

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2
Q

Identify 3 common organisms which cause TB

A
  • M tuberculosis (most common)
  • M bovis
  • M africanum
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3
Q

Describe the structure of mycobacterium tuberculosis

A
  • Non-motile rod-shaped bacteria
  • Obligate aerobe
  • Long-chain fatty acids (structural rigidity)
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4
Q

How is TB transmitted?

A

Spread is by respiratory droplets e.g. coughing, sneezing, etc

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5
Q

How easily can TB be transmitted?

A
  • Contagious, but not easy to acquire infection
  • Prolonged exposure facilitates transmission (at-least 8 hours/day up to 6 months)
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6
Q

In 6 steps, outline the pathogenesis of TB

A

⇒ Inhaled infectious droplets

⇒ Engulfed by alveolar macrophages

⇒ Travels to local lymph nodes

⇒ Primary complex (primary infection – Ghon’s focus)

⇒ Initial containment of the infection (latent infection)

⇒ Either: heals/self cure (95%) OR reactivates to post primary TB

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7
Q

What is a Ghon’s focus?

A

Ghon’s focus is a calcified tuberculous caseating granuloma which represents the sequelae of primary pulmonary tuberculosis infection

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8
Q

Distinguish between Latent TB and TB disease in terms of the following:

  • Activity
  • Chest X-Ray
  • Sputum
  • Symptoms
  • Transmission
  • Testing
A
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9
Q

What is post-primary TB?

A
  • Post-primary tuberculosis is a condition which usually occurs during the two years following the initial infection (can occur at any point)
  • Reactivation frequently occurs in the setting of decreased immunity and usually involves the lung apex
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10
Q

What is latent TB?

A

A latent tuberculosis infection (LTBI) is a condition wherein a patient is infected with Mycobacterium tuberculosis, but the infection is contained by the host’s body and is not active

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11
Q

Identify 5 risk factors for the reactivation of latent TB

A
  • HIV infection
  • Substance abuse
  • Prolonged corticosterioid therapy
  • Diabetes Mellitus (poorly controlled)
  • Organ transplant (immunosuppression)
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12
Q

Describe the pathology & histology of tuberculosis

A

A caseating granuloma appears in the lung parenchyma and mediastinal lymph nodes

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13
Q

Identify the sites of pulmonary, extrapulmonary and miliary TB respectively

A
  • Pulmonary TB: lungs
  • Extrapulmonary TB: larynx, lymph nodes, pleura, brain, kidneys
  • Miliary TB: all other parts of the body (through the bloodstream)
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14
Q

Most cases of TB are pulmonary and miliary TB is rare.

When is extra-pulmonary TB most commonly seen?

A
  • HIV-infected
  • Immunosuppressed persons
  • Young children
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15
Q

Outline the clinical approach for a patient with suspected TB

A
  • Index of suspicion
  • Suggestive symptoms (history)
  • Investigations
  • Treatment
  • Prevent transmission
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16
Q

Identify 5 groups of people in whom one should suspect TB

A
  • Non-UK born/recent migrants (South Asia/Sub-Saharan Africa)
  • HIV
  • Immunocompromised people
  • Homeless
  • Drug users
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17
Q

Identify 5 key parts of the history of a patient with suspected TB

A
  • Ethnicity
  • Travel history (high TB burden countries)
  • Contacts with TB
  • BCG vaccination?
  • Specific clinical features
18
Q

Identify 5 symptoms of TB

A
  • Fever
  • Night sweats
  • Weight loss and anorexia
  • Tiredness and malaise
  • Cough (haemoptysis occasionally)
19
Q

Identify 5 signs of TB

A
  • Pyrexia
  • Weight loss
  • CXR abnormality
  • Crackles in affected area
  • Fibrosis (in extensive disease)
20
Q

Identify 4 investigations one can request for when treating a patient with suspected TB

A
  • Chest X Ray
  • Sputum (3 early morning samples)
  • Induced sputum
  • Bronchoscopy
21
Q

Why is the apex of the lung often affected by TB?

A

The apex of the lung is the most oxygenated region of the lung and Mycobacterium tuberculosis is an aerobe

22
Q

Describe the radiological appearances of TB

A
  • Ill-defined patchy consolidation
  • Cavitation develops within consolidation
  • Healing results in fibrosis
  • Pleural effusion (if pleural involvement)
23
Q

Identify 5 laboratory tests used for TB

A
  • Sputum culture (gold standard)
  • Gastric acid aspirates (in kids)
  • NAAT
  • Chromatography
  • Drug sensitvity (for treatment)
24
Q

What is the tuberculin sensitivity test?

A

TST/ Mantoux test is a diagnostic test for TB wherein tuberculin is injected into the patient intradermally to observe a skin reaction if one has been exposed to TB

25
Q

What are the problems with the Mantoux test?

A
  • False positives (BCG)
  • False negatives (immunocompromised – HIV/drugs)
  • Subject to interpretation
26
Q

What is involved in interferon gamma releasing assays?

A

Detection of antigen-specific IFN-gamma production

27
Q

What are the problems with interferon gamma releasing assays?

A
  • Cannot distinguish latent & active TB
  • Similar problems with sensitivity & specificity
28
Q

What are the three ways of treating TB?

A
  • Multi-drug therapy (RIPE)
  • Vitamin D
  • Surgery
29
Q

TB treatment involves early and adequate treatment with anti TB drugs.

Outline the multi-drug therapy in TB as well as the associated side effects (RIPE)

A
  • Rifampicin – raises transaminases & induces cytochrome P450 (orange secretions)
  • Isoniazid – peripheral neuropathy & hepatotoxicity
  • Pyrazinamide – hepatotoxicity
  • Ethambutol – visual disturbance
30
Q

Describe the duration of TB treatment

A
  • 3/4 drugs (2 months)
  • Rifampicin & Isoniazid (4 months)

18 months if CNS TB

31
Q

How does one ensure adherence to TB medication?

A
  • Directly observed therapy (DOT)
  • Video observed therapy (VOT)
32
Q

What are the two types of drug resistant TB?

A
  • Multi-drug resistant TB (MDR) – resistant to rifampicin & isoniazid
  • Extremely drug-resistant TB (XDR) – also resistant to fluoroquinolones & at least 1 injectable
33
Q

What causes drug resistant TB?

A
  • Spontaneous mutation
  • Inadequate treatment
34
Q

What increases the likelihood of drug resistant TB?

A
  • Previous TB treatment
  • HIV infection
  • Known contact of MDR TB treatment
  • Failure to respond to conventional
35
Q

What is miliary tuberculosis?

A

- Miliary tuberculosis (TB) is the widespread dissemination of Mycobacterium tuberculosis via haematogenous spread

  • It occurs either during primary infection or during reactivation and often multiple organs involved (including the lungs)
36
Q

Which systems are often affected in extra-pulmonary TB?

A
  • Lymphatic system
  • GI system
  • GU system
  • MSK system
  • CN system
37
Q

How does lymphadenitis present in extra-pulmonary TB?

A
  • Scrofula
  • Cervical lymph nodes (most commonly)
  • Abscesses & sinuses
38
Q

Describe how extra-pulmonary TB affects the genitourinary system

A
  • Slow progression to renal disease
  • Subsequent spreading to lower urinary tract
39
Q

Describe how extra-pulmonary TB affects the musculoskeletal system

A
  • Spinal TB (most common)
  • Pott’s disease
40
Q

Describe how extra-pulmonary TB affects the central nervous system

A
  • Chronic headache
  • Fevers
  • Lymphocytosis
41
Q

Describe the principles of controlling TB

A
  • Detection and treatment of cases and contacts
  • Prevention of transmission: PPE, negative pressure isolation
  • Reduce susceptible contacts: address risk factors, vaccination
42
Q

What is the BCG vaccine?

A

BCG vaccine is a vaccine primarily used against tuberculosis wherein a live attenuated M. bovis strain is injected into babies in high prevalence communities only

(LUSUMA) Respiratory System (19 decks)

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