Tuberculosis

Question 1

what stain is utilised for Mycobacterium tuberculosis, and why?

Answer 1

• Ziehl-Neilsen stain used for acid fast bacilli

- pink

Question 2

transmission & entry

Answer 2

via respiratory tract, aerosols/droplets

Question 3

pathenogenesis - how does it survive within macrophages

Answer 3

• maintains phagosome pH at 6.2-6.3 for replication

- inhibits lysosome fusion within macrophage

Question 4

pathenogenesis

Answer 4

• survives inside macrophages
• produces granuloma (survival niche)
• can establish an asymptomatic latent infection

Question 5

tuberculin skin test (TST)

Answer 5

• inject purified protein derivative (PPD) & tuberculin

- induces local inflammatory response and recruits CD4+ cells

Question 6

IGRA (interferon production in response to in vitro stimulation with specific M. tuberculosis antigens)

Answer 6

• collect patient’s blood to add to culture medium
• add PPD
• test for interferon secreted into media

Question 7

if positive for TST or IGRA…

Answer 7

• chest x-ray

- microscopy of sputnum