Tuberculosis (TB) Flashcards
(31 cards)
Which bacteria causes tuberculosis?
Mycobacterium tuberculosis complex
Who is at a higher risk of developing tuberculosis?
- Diabetics
- HIV/cancer/organ transplants
- Immuno-suppressed patients
- Excessive alcohol/smoking
What is the difference between active and latent TB?
Active TB: illness can occur weeks, months or years after inhaling in the bacteria
Latent TB: no illness and not infectious, the immune system regulates TB to minimal levels. It can also reactivate later in life
- Remember active TB is always symptomatic
Which vaccine is given for tuberculosis?
BCG vaccine.
Which certain populations are offered the TB vaccination?
- Born in an area where TB is high
- Working with animals that can also get TB e.g. chimps or cows
- <15years who werent vaccinated as newborn babies
- Been in close contact with someone who has had TB
What are some symptoms of active TB?
- Persistent cough with/without sputum, may contain blood
- Loss of appetite/losing weight
- Extreme fatigue
- Fever with sweats
What does the physical diagnosis of active TB depend on?
If the TB is:
- Pulmonary
- CT scan, x-ray - In the lymph nodes
- MRI, CT scan - In the bones
- X-ray, CT, MRI
All specimens are also taken for microscopy/histology
What is the mantoux test for latent TB?
It is a TB skin test where tuberculin is injected and the skin is inspected for a reaction.
Positive test: if the reaction is >5mm
How can a false positive test occur during the mantoux test?
The irritation produced could be from something else other than the tuberculin injected.
What is the interferon gamma release assay (IGRA) test for latent TB?
it is a blood test to detect the response of WBC’s to TB antigens.
What are the benefits of the IGRA test compared to the mantoux test?
False positive results are less likely to occur, and the results are much quicker.
How is the mantoux test administered?
Via intradermal injection.
What can happen after, if the mantoux test has turned out positive?
- Assess for active TB
- Consider IGRA test for more evidence
- Offer treatment for a latent infection
What are the treatment options for latent TB?
- Sometimes does not have to be treated
- 3 months isoniazid (300mg daily) + rifampicin (600mg daily) + pyridoxine hydrochloride (vit. B6, 10-20mg daily)
- OR 6 months isoniazid (300mg daily) + pyridoxine hydrochloride (vit. B6, 10-20mg daily))
Why is pyridoxine hydrochloride (vit. B6) given with isoniazid?
It prevents induced neuropathy
What is the mode of action of rifampicin?
It inhibits DNA-dependent RNA polymerase activity, so suppresses RNA synthesis and is hence bactericidal.
How is rifampicin taken in TB?
Taken on an empty stomach to allow efficient absorption.
Why can drug interactions occur when taking rifampicin?
Because rifampicin is a CYP450 inducer.
What is the mode of action of isoniazid?
It interferes with the cell wall synthesis and is hence bactericidal (bacteriostatic in low conc.)
What should be monitored when taking isoniazid for TB?
Liver function.
What occurs in the GI when pyridoxine hydrochloride (vit. B6) is given?
It is converted into its active forms
What is the standard treatment of active tuberculosis?
- INITIAL PHASE: REMEMBER ‘RIPE’
- 4 drugs for 2 months
- Rifampicin
- Isoniazid (+ pyridoxine hydrochloride, vit. B6)
- Pyrazinamide
- Ethambutol hydrochloride - CONTINUATION PHASE
- 2 drug for 4 months
- Rifampicin + isoniazid + pyridoxine hydrochloride
- Those with active CNS TB need to extent their treatment for 10months
What test needs to be regularly conducted when taking ethambutol in active TB?
Eye assessments, to avoid severe ethambutol/isoniazid interactions (optic neuropathy)
What needs to be monitored when taking pyrazinamide for active TB?
Hepatic function.
