3- TB Flashcards
what are organisms are part of mycobacterium tuberculosis complex?
-m.tb
-m.africanum
-m.bovis
what is the importance of the size of mycobacterium tuberculosis?
they are very short rods (2-4 microns in length) - when we cough, aerosols droplets are 2 microns (these are things that are too big too go away but too small to fall so stay in air)
what is latent TB infection?
TB inside body but not causing any symptoms - can recognise with skin test (old-fashioned test)
→TB in dormancy in cells
in a house with Tb does everyone get sick?
no
50% don’t even get sick, 5% get sick quickly, 5% get sick later
*important for understanding - for TB control
who gets TB?
- people who meet people who have TB (within 5 years) and even more likely if person you met was smear+ (bug in sputum) and obviously more likely if close contact over casual contact
- immunosuppressed e.g. HIV
- social deprivation
- immigrants (higher likelihood if moved within last 5 years from country with high TB rate to country with lower TB rate)
- high in young kids, late 20s, much older people who are exposed to TB
what are the majority of TB cases due to?
The majority of TB disease is re-activated disease in individuals previously entering the country with latent TB infection
where does TB affect?
any organ of body, most commonly the lungs (50%)
what are symptoms of TB?
- weight loss
- night sweat
- malaise
- fever
- specific symptoms + signs specific to organ
what are signs of TB to look for on chest x-ray?
- look for cavity
- look for tree & bud (pus in airways)
what is the common site of TB reactivation? (waking up from latency)
apical and posterior segments of the upper lobes and the superior segments of the lower lobes
what are the types of TB that have least to most effective host immune response? (7 types)
- Miliary TB= form of TB where tiny droplets of TB spread through body in blood and caught in lungs - making look like liver
- Meningeal TB = when infection of membranes surrounding brain + spinal cord
- Pulmonary (widespread) = form affecting lungs extensively
- Pulmonary (localized) = infection more specific to lobe or area of lung
- Localised Extrapulmonary = infection outside the lungs affecting other organs or tissues
- Lymph node
- Healthy contact (latent TB infection - LTBI) - have been exposed but not developed active disease, generally body immune response effective at containing
what are classical microbiology and histology tests?
- specimen testing (sputum etc)
- procedures like microscopy using ZN or auramine stains
- culture
- histology
what are the gold standard microbiology tests for TB?
cultures = done on both solid + liquid phase, drug sensitivity tests can be done too
what is good about histology test for TB?
allows visualisation of granulomas with central caseous necrosis = key characteristic of TB
TB switches off genes and goes to sleep but host not strong enough to completely remove. when TB wakes up (if host gets weaker) then it escapes. This makes granulomas necrotic (as break down)
what specimens can be used for TB testing?
- Sputum x3, gastric washings (fluid collected in lungs, when sputum not adequate), bronchoalveolar lavage (washing out portion of lung’s airway)
- early morning urines x3
- biopsies = tissues samples
