Tuberculosis Flashcards
What is mycobacterium tuberculosis (MTB)?
- pathogenic bacteria
- aerobic bacteria hence why they affect the lungs
- can be Gram - or + due to waxy cell coating
- generally classed as - though
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What is atypical non-mycobacteria?
- part of mycobacterium family (cousin of TB)
- opportunistic bacteria
- effect immunocompromised patients
TB is the most common cause of infectious related mortality disease worldwide. Approximately how many people worldwide have latent TB?
- 2.3 billion - global incidence is falling
Is there an interaction between TB and HIV?
- yes, TB affects those immunocomprimised
- HIV patients have low CD4+ T cells
- HIV patients are unable to mount an immune response
- always test for HIV when suspecting TB
TB rates are reducing, but still have a high incidence in some places, especially those with low socio-economic countries. What is the definition of high incidence?
- 40 per 100,000
Why is TB more common in big cities?
- ⬆️ ethnic diversity - people acquire TB and move to UK - majority of TB patients in UK, are born outside UK
Which patients are at greater risk of developing TB?
- deprivation (malnourished, overcrowding) - alcohol - prisons - immunocompromised - elderly - high risk groups (jobs)
How is TB transmitted?
- through airways (80% affects lungs)
Once inside the lungs how can TB spread through a specific type of immune cell?
- macrophages ingest TB and attempt to phagocytose
- if macrophage cannot phagocytose TB can replicate in endosome
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What amount of the worldwide population have latent TB?
- 1/3 - 10% of this 1/3 will develop active TB
If TB becomes active and is not contained it can spread to the rest of the body, what does haematogenous mean?
- infection spread through blood
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If TB becomes active and is not contained it can spread to the rest of the body, what system other than circulatory can it used to spread?
- lymphatic system - can enlarge lymph nodes
In addition to spreading through lymphatics and blood, how else can TB spread?
- direct contact - pericardium could be affected
What are common clinical presentations of pulmonary TB?
- THINK TB
- cough (not improving with antibiotics)
- haemoptysis (coughing up blood)
- chest pain and breathlessness
- fever / night sweats
- fatigue and weight loss
What does the mnemonic THINK TB when diagnosing TB mean?
- T = troublesome cough
- H = haemoptysis
- I = involuntary weight loss
- N = night sweats and fever
- K = known exposure to TB
- T = tiredness
- B = breathlessness and chest pain
What other disease does TB present clinically similar to?
- sarcoidosis
What is erythema nodosum commonly seen in TB and Sarcoidosis?
- erythos = greek for red - red and raised tender rash on the skin (generally legs) - acute presentation
What is Phlyctenular conjunctivitis commonly seen in TB and Sarcoidosis?
- red and inflamed eye
When a patient is comes into contact with TB and acquires it, macrophages digest and try to phagocytose it. Following this is can become one of 2 things, what are they?
- active - latent
If TB becomes latent what are the 2 things that can occur?
- lungs heal and eradicate TB
- re-activation when patient is immunocompromised
If a patient becomes infected with TB that the immune system is not able to develop a granuloma, what happens in the short term to the patient?
- TB symptoms present
- TB can then disseminate to lungs
- TB can spread to the whole body (miliary)
What is the granuloma surrounding the TB infection called?
- Ghon Focus
- small foci on lungs
In addition to forming a Ghon foci (granuloma) where else can then granuloma overlap to or immune cells spread the TB?
- lymph nodes at the hilum primary bronchi enter lungs
- these lymph nodes become inflamed
If the Ghon foci overlap onto a hilar lymph nodes, what is this complex called?
- Ghon complex
What is the term given to the tissue within the granuloma surrounding the TB?
- necrotic tissue (dead)
- caseous necrosis (cheese like)
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What happens to Ghon complex that allows them to be identified on chest X-rays?
- undergo fibrosis and/or calcification
- this can be seen on an X-ray, called a Ranke complex
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When TB is surrounded by the granuloma, do they always die?
- some can die
- some remain latent
If the acute TB infection cannot be surrounded by a granuloma, what can happen to the infection?
- disseminate (spread) throughout lungs
- it can can spread to whole body, called miliary TB
What does miliary TB mean?
- TB infection has spread systemically to whole body
Out of all people who are exposed to TB, what % will develop a primary and latent infection?
- primary = 5%
- latent = 95%