Tuberculosis (Respiratory) Flashcards
What findings would someone with TB have on bronchoscopy?
Tubercles and pus.
How long does it take to cure TB?
6 months.
Where is there quite a lot of TB?
Eastern Europe, Africa and Asia.
Describe the development of TB after infection with mycobacterium tuberculosis.
TB enters airway and then alveoli. Forms granulomas in the alveolus which contain the bacterium. If the bacteria break out of this granuloma then disease occurs.
When people are infected with TB, what are the percentage chances that they will remain well or develop the disease?
90% remain well, 5% get primary TB and 5% get reactivation of latent disease.
What are the symptoms and signs of TB?
General: weight loss, malaise, night sweats. Respiratory symptoms and signs: cough, haemoptysis, breathlessness, upper zone crackles. Meningeal: headache, drowsy, fits. GI: pain, bowel obstruction, perforation, peritonitis. Spinal: pain, deformity, paraplegia. Lymphadenopathy. Cold abscess. Pericardial: causes cardiac tamponade. Renal: renal failure. Septic arthritis: cold monoarthritis of large joints. Adrenal: hypoadrenalism.
How long does ZN staining take?
A lot of time.
If someone is smear negative but culture positive, are they regarded as infectious?
No as the number of mycobacterium in their sputum is tiny.
What is the most to least sensitive tests for TB?
Culture (picks up other mycobacteria, gives full range of sensitivities) -> PCR -> ZN stain.
What antibiotic is TB resistant to?
Rifampicin.
What is the histology of TB?
Multinucleate giant cell granulomas, caseating necrosis, sometimes visible mycobacteria.
On CXR, what are the key characteristics of TB?
Upper lobe predominance, cavity formation, tissue destruction, scarring and shrinkage, heals with calcification.
What is miliary TB?
When it gets in the bloodstream and goes everywhere in the chest. Looks like metastatic renal cancer.
What is the therapy for TB? (important)
2 months of rifampicin, isoniazid, purazinamide, ethambutol. 4 months of rifampicin, isoniazid.
What can aid adherence of TB tablets?
Combination pills.
What are the side effects of rifampicin?
Colours urine and all bodily fluids orange. It is also a potent inducer of cytochrome enzymes which cause rapid breakdown of all steroid molecules including hormonal contraception and similar breakdown of opiate analgesics and many other drugs.
What is a side effect of ethambutol?
Can cause optic neuritis (inflammation of optic nerve).
How do you know if someone can move down from 4 drugs to 2?
There spit should be a negative test (may be some nonreplicating bacteria but not many replicating).
What types of drug resistant TB are there and what are they resistant to?
Single agent (commonly isoniazid), multi-drug resistant (MDR, rifampicin and isoniazid), extended drug resistant (XDR, MDR and quinolone and injectable).
What is the criteria for latent TB?
No evidence of active TB e.g. symptoms, x-ray, culture. Evidence of previous TB infection e.g. history of TB prior to 1960, calcification on x-ray, exposure to high prevalence area.
What tests are there for latent TB?
Interferon gamma release assay (blood test) (IGRA), detects previous exposure to TB. Mantoux (tuberculin) test (skin test) - detects previous exposure to TB and BCG.
What are the downsides to the tuberculin skin test (Mantoux)?
2 visits, intradermal injection, false positive if BCG vaccination given, cannot distinguish latent TB, cured TB, active TB or BCG.
Describe the IGRA test.
Good for mass contact tracing but very expensive, looks for interferon gamma specific to antigens found only in m.tuberculosis.
If someone has latent TB and you want to give them anti-TNF drugs what else would you give them?
6 months of isoniazid or 3 months of rifampicin and isoniazid.
