Bee, there isn't really a "protocol" per say, but IME there does seem to be a connection between healthy diets with lots of cultured live foods and lower incidence of GBS. So for mom's with a history of being GBS+, or who are really worried about it, I encourage them to take lots of *live* yogurt and also maybe supplement with capsules toward the end of pregnancy. It's really important that the yogurt "contain" live cultures and not simple be "made" with live cultures. Unfortunately most of the stuff at the grocery does not contain live cultures.
I actually swabbed myself this week. If I test postive I am going to hit the lactos hard (4 caps a day oral, 2 caps vag) and re-test. Using a negative test after a positive is not in accordance with CDC guidelines on the issue but fortunately my MW is willing to go with the plan and document a negative if I get it. As with you, I am only screening in hopes of documenting a negative in case of transfer. Yes, I have encountered a few GBS-sick babies, but to me this risk is so small, and definitely not worth dealing with antibiotics in labor, or the antibiotic aftermath on my and my baby's system.