Glad Sutton is doing well, Pneumaticmatt! :) I hope that he will continue to be healthy, and I hope that he is not in any pain right now.
Definitely agree with Galahad about the probiotics, but I would also agree to wait until his prescription is finished to avoid infection.
If he can tolerate it, maybe you could try including anti-microbial foods like ginger and garlic into his diet, if he can tolerate them? I don't know about post-surgery recovery, but they help me whenever I have a sinus infection. Plus they're great for overall health.
Best of luck for Sutton! :)