Sani-
My sister, a naturopath, suggested I to try antibiotics first
(I'm also trying the no-starch diet), and then proceed with probiotics.
First try to rid your intestines/body of the possible bad bacteria (the "bad ones" for AS sufferers), then try to re-populate with good ones (via probiotics).
There are many discussions on probiotics/antibiotics on the forums here, just put the words in the search field on the left.
I'm seeing yet another doctor next week, and will ask about antibiotics then...
/Kristine