Epidemiology of Tuberculosis
Where in the UK has the most number of TB cases?
London
- due to multi-ethnic backgrounds
- condensed living spaces
What type of bacteria is M. tuberculosis
obligate intracellular bacteria
Once inhaled where does M. tuberculosis migrate to
What type of hypersensitivity reaction does the Tuberculin Skin Test rely on?
- type 4 hypersensitivity
What drug turns bodily fluids orange?
- rifampicin
Where in the UK has the lowest number of TB cases?
- East Midlands
What does M. tuberculosis replicate inside of?
macrophages
Having what condition increases a persons relative risk of having TB by 100x
HIV
Explain the results of the Tuberculin Skin Test
- inject M. tuberculosis antigens intradermally
- wait 48 hours
- if body has already been exposed to TB the immune system will recognise the antibodies and a 'lump' will form at injection site
- if no prior exposure then body will not produce a lump; due to body not recognising the antigens
Explain how medications may be affected when taking rifampicin
- rifampicin is a potent cytochrome P450 inducer
- interacts with a lot of medications
(may need to up the doses of medications)
Where globally has the highest rates of TB?
southern hemisphere
- places in Africa
- South East Asia
Why is TB hard to diagnose (from a microbiology perspective)
- M. tuberculosis is slow growing
- so hard to obtain appropriate sample
(plus poor sensitivity of diagnostic tests)
What type of necrosis is seen in TB infections
caseous necrosis
Explain the IFN-g release assay
- blood test
- measures body's immune responce to M. tuberculosis
- quantifies amount of IFN-g released by T cells
- in responce to M. tuberculosis antigens
First line treatment for TB
- RIPE
- rifampicin + isoniazid for 6 months
- pyrazinamide + ethambutol for the first 2 months
Why are there higher incidence rates of TB in lower income countries?
- poor health care systems
- HIV epidemics
Apart from M. tuberculosis, name another pathogen causing Tuberculosis and how you can contract it
- M. bovis
- from drinking unpasteurised cow milk
Which cytokines are involved in immunity of TB
- IFN-g
- TNR-a
When may you consider surgery to treat TB
- when a person has XDR-TB
- no medications will treat it
Second line drugs used to treat TB
- bedaquiline
- linezolid
- delaminad
- b-lactams
In what populations does TB spread?
- urban poor
- alcoholics
- IV drug users
- homeless
- prison inmates
What can manifest from M. tuberculosis being inhaled?
- cleared from the body (90%)
- heal with scaring -> Gohn focus
- lie dormant
- primary progressive disease
What is the significance of CD4+ cells in Tuberculosis
- macrophages process and present M. tuberculosis antigens
- T cell receptor on CD4+ cell recognise antigens, produce INF-g
- which trigger immune responce
What is pyridoxine and when may you want to give it
- Vit B6 supplement
- give to people taking isoniazid
Define MDR-TB and XDR-TB
TB that is resistant to isoniazid and rifampicin
TB that is resistant to
- any fluoroquinolone and
- either linezolid or bedaquiline
- in addition to MDR-TB