Sorry I'm no help with the tea tree oil remedy, hopefully someone here will have more info for you. You might also want to check out old gbs threads on the midwife board.
I just want to take this opportunity to say that I refused the test (along with most others, afp, gd, etc.) initially, then caved in to pressure from my cnm on the gbs.
This mistake led to a nightmare induction, and caused problems for my little one, giving him a rocky start in life. I would NOT recommend this latest fad test for anyone. I know you've already done it, and my advice is late for you, hopefully other moms reading this will reconsider and do more research before consenting to the test.
Wishing you the best, and hopefully you'll get helpful info on the midwife/doula thread!