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
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
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
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)
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
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%