What amounts and which types of probiotics are recommended in pregnanc

I am 26 weeks pregnant with my third child and a recent test showed I had GBS infection. I currently live outside the US and my local doctor has recommended I take antibiotics. From everything I read on the Internet, their use to treat GBS during pregnancy is not recommended. The doctor laughed at the notion of having them administered intraveinously during labor, so I have decided to do all my best to obtain negative results before my next test at 35 weeks. I want to order some probiotics from the US, but don't know what I should look for. What brands, what kinds of strains, what amounts should I be looking for? Any other suggestions in fighting GBS naturally would be greatly appreciated. Many thanks.