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Respiratory > TB > Flashcards

TB Flashcards

0
Q

What happens to the aerosolised droplets?

A

Droplets evaporate to form droplet nuclei which disperse in the air without settling
The organisms they contain remain viable for extended periods of time

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1
Q

How is TB transmitted?

A

Between people via aersolised droplets

They are produced in coughing, sneezing, talking etc.

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2
Q

How are the droplets eventually eliminated?

A

Infinite dilution

UV radiation

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3
Q

What happens when the mycobacteria droplets reach the pulmonary alveoli?

A

Engulfed by alveolar macrophages
Mycobacterium replicates within them.
Macrophages carry the bacteria to hilar lymph nodes to try and control the infection.

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4
Q

Why are macrophages unable to kill mycobacteria?

A

The bacteria’s cell wall contains lipids which block fusion of phagosomes and lysosomes

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5
Q

How does a granulomatous reaction occur?

A

Macrophages ingest mycobacterium

Lymphocytes and fibroblasts surround the infected macrophages to prevent dissemination of bacteria

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6
Q

What is caseous necrosis?

A

Epithelioid macrophages, Langerhans giant cells and lymphocytes surround a cheese-like core of necrosis
Form a tubercle

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7
Q

What forms the primary complex?

A

Ghon’s nodes - sub pleural focus of tubercles

Draining lymph nodes

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8
Q

Classifications of mycobacterium tuberculosis?

A

Bacilli, aerobic, acid and alcohol fast

Slow growing on culture (2-6 weeks)

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9
Q

Why are mycobacteria Gram resistant?

A

Cell wall is hydrophobic

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10
Q

How does haematogenous spread occur?

A

Before healing of the primary complex the TB bacilli can enter the bloodstream and sorehead to other parts of the lung and other organs (extra-pulmonary sites)

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11
Q

What is latent TB?

A

When the primary infection is contained, primary complex heals but some organisms remain viable

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12
Q

What can cause deactivation of latent TB?

A

When immune system is compromised

HIV, age, malnutrition, immunosuppression

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13
Q

What does latent TB become if reactivated?

A

Primary progressive TB

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14
Q

What happens to the granulomas in primary progressive TB?

A

They form but necrotic tissue undergoes liquefaction and the fibrous wall breaks down.
Necrotic material drains into the bronchi, is coughed up and can infect others.
Can drain into blood vessels and become extra-pulmonary TB.

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15
Q

What is primary TB?

A

When you get formation of the primary complex and it resolves with local scarring

16
Q

Where does primary infection of TB commonly occur?

A

Upper lobe

17
Q

Why is post-primary pulmonary TB common in the upper lung zones?

A

High ventilation/perfusion

High pO2

18
Q

What can post-primary pulmonary TB lead to and how?

A

Proliferation of TB bacilli in caseous centres followed by softening and liquefaction of caseous material
Can discharge into the bronchus and cause cavity formation
Fibrous tissue forms around periphery of TB regions but unable to limit extension of TB process
Haemorrhage of caseous process into vessels in cavity walls - haemotypsis

19
Q

How does post primary pulmonary TB lead to TB pneumonia?

A

Get spread of caseous/liquefactive material through the bronchial Rees causing infection in other lung zones
See lots of inflammatory exudate which fills the alveoli to form pneumonia

20
Q

How does miliary TB occur?

A

When you get rupture of caseous pulmonary focus into a blood vessel
Get formation of miliary TB foci in lung and other organs.

21
Q

Signs and symptoms of TB?

A 
Persistent cough
Haemotypsis
Shortness of breath
Fever and chills
Fatigue
Loss of appetite and weight loss
Lymphadenopathy
22
Q

What can be seen on a CXR?

A

Pulmonary shadowing which be patchy, solid lesions

Streaky fibrosis or flecks of calcification

23
Q

How is latent TB diagnosed?

A

Positive tuberculin skin test

Patient has type IV hypersensitivity reaction to proteins derived from mycobacteria

24
Q

Treatment of TB?

A

First 2 months - rifampicin, isoniazid, pyrazinamide, ethambutol
Continuation phase, next four months - rifampicin and isoniazid

25
Q

What would suggest a case of multi-drug resistant TB (MDRTB)?

A

History of previous incomplete treatment
Residence in a country with high incidence of MDRTB
Failure to respond clinically to an adequate regimen

26
Q

What is the BCG vaccine prepared from?

A

Attenuated live bovine tuberculosis bacillus

27
Q

Issues with BCG vaccination?

A

Not always effective

Only provides protection for 15 years

28
Q

Which groups are high risk for TB?

A 
HIV
IV drug use
Malnutrition
Overcrowding
Ethnic minorities
Chronic lung disease
Immunosuppression
29
Q

What is post-primary TB?

A

Development of TB beyond the first few weeks of infection

30
Q

What does the immune response to post-primary TB cause?

A

Local tissue destruction (cavitation in the lung)

Cytokine-mediated systemic effects such as weight loss and fever

31
Q

What can extra-pulmonary TB cause?

A

Can affect every organ
TB meningitis - fever and deteriorating level of consciousness
Kidney infection
Lumbosacral spine can be infected - vertebral collapse and nerve compression
Inflammation of large joints - destructive arthritis

32
Q

What causes the formation of granulomas?

A

Release of IL-12
Drives release of IFNγ and TNFα from NK and CD4 cells
Activates and recruits more macrophages to site of infection, causing granuloma formation

33
Q

Symptoms of primary TB?

A

Few symptoms

Enlarged lymph nodes

34
Q

What are the two types of osteo-articular TB?

A

Tuberculous spondylitis

Poncet’s disease

35
Q

Describe the pathology of tuberculous spondylitis

A

Begins in subchondral bone and spreads to vertebral bodies and joint space, following the anterior and posterior longitudinal ligaments of the spine
Mainly occurs in lower thoracic and lumbar spine

36
Q

What is Poncet’s disease?

A

Asceptic arthritis

Occurs in knees, ankles and elbows

Respiratory (17 decks)

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