lecture 16 - tuberculosis Flashcards
What is tuberculosis?
An infectious bacterial disease caused by strains of Mycobacterium tuberculosis
What is the shape of Mycobacterium tuberculosis bacteria?
Bacillus
Are mycobacteria gram negative or positive?
Neither - they are acid-fast
How is TB spread?
Via aerosols & droplets
What is primary/progressive primaryTB?
Infection with TB where the disease develops straight away, rather than becoming latent after the immune system deals with the initial infection
What is the outcome for the majority of people who become infected with TB?
They will have an initial lesion form and then latent infection until it is reactivated in a small number of people causing post-primary TB
What happens to M tuberculosis cells when they reach the alveoli and encounter immune cells?
They are phagocytosed by macrophages and packaged into the phagolysosome, however, the bacteria may be resistant to this
What is the name for the first lesion that forms with TB infection?
Granuloma/Ghon Focus
What processes form the granuloma in initial TB infection?
Macrophages encountering TB release cytokines to attract more macrophages and T cells, which cause an inflammatory response that forms a granuloma
What 2 cytokines are most important in TB granuloma formation?
TNF-alpha, IFN-gamma
How does the initial TB solid granuloma facilitate dormancy of the infection?
It has hypoxic conditions and nutrient limitation, meaning the TB may survive but have difficulty replicating
How can patients be tested for Latent TB infection?
With a Tuberculin skin Test (i.e. Mantoux test), or Interferon Gamma Release Assay
How does the Mantoux test identify latent TB?
Patient is injected with tuberculin which will trigger a hypersensitivity reaction in patients with previous exposure to TB
What are some of the limitations of the Mantoux test?
Cross-reactivity with vaccines and non-tuberculous mycobacteria
