Actually, there are ways to eliminate it before delivery.
You can up your probiotics and fermented foods (like sauerkraut), take immune boosters (like Vitamin C, garlic and echinacea), you can insert garlic vaginally, use hibiclens, and keeping vaginal examinations to a minimum.
I'm not saying don't take the antibiotics if that's what you're comfortable with. I'm a firm believer in everyone making the best choice for themselves. :)
I'm just putting it out there that there ARE options you can try prior to testing and up until labor to remain GBS negative.
Boosting your immune system is the best way to keep it at a level that is healthy and would return a negative test and to lower your chances of it returning.
My labors are so short I don't really have the option of antibiotics in labor. DS2 was born in 45 minutes and in 18 minutes after my water broke. Not even enough time for the midwives to show up which is why I choose to boost my immune system as much as possible. Taking antibiotics prior to labor is not going to help a GBS+ patient as it will have plenty of time to return before labor begins. If I were choosing the antibiotic route again, I'd choose it during labor rather than weeks prior.
There are tons of links out there for natural remedies for GBS as well as tons of threads on MDC for it.
Anilia - They won't test you again at 35-37 weeks just because you were positive in early pregnancy?