Yes, depending on the type of MAC infection and your status, which would include the CT scan results and how you are feeling, "watchful waiting" is an acceptable choice for many. Some things to consider are; how is your health other than this present concern? Are you having lots of symptoms? Have you been ill with lung infections like Pneumonia? Do you have a chronic cough? Are you doing airway clearance? These are all things to be considered as well as what your CT scan shows. It is best to consult with a Pulmonologist that is knowledgeable and practiced in caring for patients with Bronchiectasis and MAC. Another consideration is that some people do not have problems with the 3 antibiotics. I do not have experience with the Big 3 (yet and fingers crossed) so I cannot speak to that. Best of luck to you and this site is a great resource for support and information. I certain others will reach out to you soon.