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Resipiratory > Session 9 - Tuberculosis, Lower Respiratory tract infection, & Pneumonia > Flashcards

Session 9 - Tuberculosis, Lower Respiratory tract infection, & Pneumonia Flashcards

1
Q

Which bacterium causes tuberculosis?

A

Mycobacterium Tuberculosis (most commonly)

  • M bovis
  • M africanum (certain cases from Africa)
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2
Q

Describe the microbiology of Mycobacterium Tuberculosis.

A
  • Non-motile rod-shaped bacteria.
  • Obligate aerobe
  • Long-chain fatty (mycolic) acids, complex waxes, and glycolipids in cell wall. (structural rigidity, can be stained)
  • Relatively slow growing compared to other bacteria.
  • Generation time 15-20h
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3
Q

How is M Tuberculosis spread?

A

By respiratory droplets, coughing and sneezing.
Suspended in the air.
Contagious but not easy to acquire infection, prolonged exposure fascilitates transmission. (at least 8 hours/day upto 6 months)

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4
Q

How does TB progress once the bacteria enter a host?

A
  1. Inhaled infectious droplets.
  2. Engulfed by alveolar macrophages.
  3. Local lymph nodes.
  4. Primary Complex
    a) 5% progress to Active disease (primary)

b) Initial containment
5. Latent infection
(i) 95% heal/ self cure
(ii) Reactivation - Post Primary TB

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5
Q

What is the difference between Latent TB infection and TB Disease (in lungs)?

A

Latent TB

  • Inactive (contained tubercle bacilli in body)
  • TST or IFN gamma tests +ve
  • Chest X-ray normal
  • Sputum cultures normal
  • No Symptoms
  • Not infectious
  • Not a case of TB

TB Disease

  • Active, multiplying tubercle bacilli in body
  • TST or blood test results usually positive
  • Chest X-ray usually abnormal
  • Sputum smears/ cultures may be +ve
  • Often infectious before treatment.
  • A CASE of TB!
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6
Q

Describe the characteristics of primary TB.

A
  • Ghon focus/ complex (Primary lesion)
  • Limited by cell mediated immunity
  • Occasionally symptomatic (miliary/ disseminated)
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7
Q

How does Post-primary TB present?

A
  • As pulmonary or extra-pulmonary.
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8
Q

What are the risk factors for reactivation of TB?

A
  • HIV infection.
  • Substance abuse.
  • Prolonged therapy with corticosteroids or immunosuppression.
  • TNF-a antagonists.
  • Organ transplant.
  • Haematological malignancy.
  • Sever kidney disease (dialysis).
  • Diabetes M.
  • Silicosis.
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9
Q

What is extra-pulmonary TB?

A

TB infection in place other than lungs.

  • Larynx
  • Lymph nodes - most commonly cervical
  • Pleura
  • Brain
  • Kidneys - slow progression, spread to lower Urinary tract.
  • Bones/ Joints
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10
Q

Which group of people are more likely to get extra-pulmonary TB?

A
  • HIV infected
  • Immunosuppressed patient
  • Young children
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11
Q

What is miliary TB?

A

TB carried through the blood stream to all parts of the body. (very rare)

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12
Q

Which people would TB be more suspected in (risk factor)?

A
  • Non-UK born/ recent migrant
  • HIV patient
  • Homeless
  • Drug user
  • Close contact (prison)
  • Younger adults (or elderly)
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13
Q

What are the symptoms of pulmonary TB?

A
  • Fever
  • Night sweats
  • Weight loss + Anorexia
  • Tiredness and malaise
  • Cough (most common)
  • Breathlessness + Pleural effusion
    (may be crackles, or cavitation/ fibrosis in extensive disease)
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14
Q

Which investigations should be done for pulmonary TB?

A
  • Chest X-Ray
  • Sputum - 3 early morning samples
  • Bronchoscopy
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15
Q

What is often seen on a CXR in TB?

A
  • Apex of lung often involved
  • Ill defined patchy consolidation
  • Cavitation usually develops within consolidation
  • Healing causes fibrosis
    (pleural effusion often seen)
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16
Q

Which lab test confirms TB is the infective organism?

A
  • Sputum culture is gold standard, up to 6 weeks of incubation.
  • Microscopy of sputum can also be done, staining for the bacilli.
17
Q

How do granuloma appear in TB in the lung? What type of necrosis is this?

A

Caseous Necrosis.

- Many immobile epithelioid histiocytes and lymphocytes surrounding a centre of caseous necrosis, usually in lung.

18
Q

Which diagnostic test is used to test if a person has been exposed to TB?

A 
Mantoux test (tuberculin sensitivity test)
Under the skin, then the size of the area is measured 48-72 hours later.
19
Q

What are the limitations of the mantoux test?

A
  • False positives (BCG vaccine, non TB)

- False negatives (e.g. immunocompromised - HIV etc)

20
Q

What are the first line drugs used to treat TB?

A
  • Rifampicin (R)
  • Isoniazid (H)
  • Pyrazinamide (Z)
  • Ethambutol (E)

For 2 months, then first 2 for 4 months.
(18 months if CNS TB)

21
Q

How is TB managed?

A
  • Early + adequate treatment with combination antibiotics (at least 6 months)
  • Close monitoring of compliance.

This makes the patient Non-infectious and there are then no secondary transmission or cases.

22
Q

Which factors increase drug resistance?

A
  • Natural mutations in replication means there are small number of drug resistant organisms.
  • Improper regimen of antibiotics or poor compliance leads to selection of the mutant bacteria.
  • Now there is a single population of multi-drug resistant bacteria.
  • Delays in diagnosis, overcrowding and inadequate infection control lead to facilitation of transmission of the drug resistance.
23
Q

What treatment is given for multi-drug resistant and extremely drug resistant forms of TB?

A

If not responding to normal regimen:

  • 4-5 Drug regimen - longer duration
  • Quinolones, aminoglycosides, PAS, cyloserine, ethionamide.
24
Q

Which organs are involved in miliary TB?

A

Often multiple organs (always lungs involved, with few resp symptoms).
Headache - meningeal
Pericardial/ pleural effusions (small)
- Ascites can be present.
- Retinal involvement (choroid tubercles seen)

25
Q

What are choroid tubercles?

A

Lesion on the retina, caused by TB bacteria.

Often cause loss of part of visual field if at macula.

26
Q

What is pott’s disease?

A

Extra-pulmonary TB in the spine, causing damage to vertebra.

27
Q

What is tuberculous meningitis?

A

Meningitis caused by M. Tuberculosis.

  • Chronic headache.
  • CSF has markedly increased proteins, and lymphocytosis.
28
Q

TB is a notifiable disease, what does this mean?

A

Must notify public health england of any cases of TB.
Triggers contract tracing procedures to track any people at risk who were in contact with the person. (try to find all the TB cases linked to the one presented)

29
Q

Why is contact tracing in TB important?

A

Treat any people at risk or who also have TB.

Provide surveillance to detect outbreaks and monitor epidemiological trends.

30
Q

What is in the BCG vaccine, how effective is it?

A

Live attenuated M. Bovis strain of mycobacterium.
70-80% effectiveness in preventing severe childhood TB.
Little evidence for adults.

Resipiratory (9 decks)

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