This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other topics and Adverse effects, Subject name: Anatomy
Once weekly administration of which of the following antibiotics has prophylactic activity against bacteraemia caused by M.avium complex in AIDS patient 
Select and explain. 
A. Azithromycin, B. Clarithromcycin, C. Isoniazide, D. Rifabutin
A: Azithromycin
Answer: A: Azithromycin 
Explanation: (Ref: KDT 6/e p730, 731) The regimen used for the treatment of Mycobacteriun avi complex in AIDS patients is REC (Rifabutin, ethambutol and clarithromycin). These drugs are given once daily. Clarithromycin can be replaced with azithromycin which is long acting and can be administered once a week.