A 53-year-old man with three months of productive cough, six kilograms of weight loss and night sweats has come to see you in a chest clinic. He has a pleasant appearance and you learn that he has recently immigrated to Hong Kong from China. In the initial investigation, a chest X-ray shows a cavitary mass in the right upper lobe, and the acid-fast bacilli (‘AFB’) smear shows positive on sputum. After six weeks, the AFB culture also shows positive.

a) Name the respiratory disease that is most likely caused by acid-fast bacteria. (2 marks)

b) List the drug regimen(s) used as first-line therapies in this patient after initial diagnosis with their mechanisms of action. (12 marks)

c) What is the rationale to use such a combination of drugs? (2 marks)

d) State the mechanism of resistance that may develop with the drugs used. (4 marks)