I was positive for GBS with my first pregnancy, and I ended up on IV antibiotics during the laboring process.
My second was born at home over 4 years later, but I saw an OB for most of my pregnancy instead of a midwife. I had a GBS test at the normal time, but it was negative. I had been using home remedies like garlic and tea tree oil topically, because I tended to have yeast issues while pregnant anyway, and the tea tree oil was really good for that. I didn't insert anything nor douche, just did topical treatments. I noticed that when I ate refined sugar, I tended to get the yeast issues, so I made sure to watch that, and with the topical treatment, my yeast issues went away long before I took the GBS test, which was negative. I gather that GBS colonization in early pregnancy can mimic yeast infection symptoms, so either way, I felt that treating it at home was better than just letting it go unchecked, even if it was just a yeast issue.
In any event, this site mentions alternative treatments for GBS colonization: http://holisticsquid.com/alternative-treatment-for-gbs/