TB Flashcards
Where is TB most common on an X-ray?
Upper zones
right
How is TB spread?
Airborne spread of mycobacterium TB
How is it usually cured?
By 6 months of antibiotics
What happens after exposure to TB?
Most people will clear the TB by the innate or acquired immune response.
Other people will be infected. Half of them will be fine and have TB infection, other people will actually have TB disease.
What does the body do with the TB?
It is taken in by the macrophage and the body seals it off in a granuloma.
When do people get active disease?
When the granuloma that the TB is in, cant hold it back anymore and the TB spreads everywhere
Name some general clinical features of TB?
Weight loss, malaise, night sweats
Name some respiratory clinical features of TB?
Cough, Haemoptysis, breathlessness, upper zone crackles
Name some meningeal clinical features of TB?
Headache, drowsy, fits
Name some GI clinical features of TB?
Pain, bowel obstruction, perforation, peritonitis
Name some spinal clinical features of TB?
Pain, deformity, paraplegia
What is a cold abscess and can you get them in TB?
are collections of pus without the pain and acute inflammation seen in a conventional abscess.
You can get them in TB
How can you test for TB?
ZN stain - due to TBs thick waxy coat (hangs onto the stain)
PCR - sputum sample. Takes 2 hours and also tells you if organism is resistant to rifampicin
Name some histological features of TB?
Multinucleate giant cell granulomas
Caseating necrosis
What are some radiological features of TB?
Upper lobe predominance Cavity formation Tissue destruction Scarring and shrinkage Heals with calcification
How do you get miliary TB?
Massive seeding of mycobacteria through the bloodstream. Untreated it can be rapidly fatal.
What is the treatment for TB?
2 RIPE 4 RI Rifampicin Isoniazid Pyrazinamide Ethambutol
What are some of the side effects of the TB medications?
Rifampicin - turns bodily fluids orange
Ethambutol - optic neuritis
Why do you need to treat TB for so long?
As there are replicating and NON-replicating TB bacilli
What is the most commonly TB drug that there is resistance to?
Isoniazid
What is commonly the MDR (multi-drug resistance) in TB?
Isoniazid and rifampicin
Describe latent TB?
Symptom free
Culture negative
It is a balance between the organisms and your immune system.
Between a quarter and a third of the worlds population has latent TB
Name some evidence that would indicate previous TB infection?
History of TB prior to 1960
Calcification on x-ray
Exposure to High Prevalence area
What tests can you do to test for previous exposure?
Interferon gamma release assay (blood test)
Mantoux (tuberculin) test (skin test) - also detects exposure to BCG
What is tuberculin?
It is a protein derived from the culture of mycobacteria. Used as a diagnostic agent.
It is only used as a diagnostic agent. 0.1ml of the solution is injected intradermally. The patient has to return at least 48 hours later to see if there has been a delayed hypersensitivity reaction at the site of injection.
How does Interferon gamma release assay (blood test)
work?
IGRA tests are performed on blood samples. The assay looks for interferon gamma specific to antigens found only in m.tuberculosis. It does not react with BCG which is an attenuated strain of m.bovis.
How might you prevent TB?
Screening of high risk subgroups
BCG immunisation
Social aspects - housing, nutrition
Describe BCG immunisation?
Attenuated strain of mycobacterium bovis
Intradermal injection
Most effective in neonates of high risk families
Also provides some protection against leprosy
What is a high risk for TB?
if you have HIV
What drugs can reactivate latent TB?
Steroids and immunosuppressant drugs
