I've done recently an extensive research on all strains of good bacteria and how it effects Candida/immunity/general well-being. Which strain survive low pH going through the stomach acid, which .... not so much. So basically what I found out is that Lactobacillus GG is the one that works for strengthening the immune system as well as helps to eliminate Candida. You can get Culturelle on Vitacost.
Another one is Lactobacillus Sporogenes which is also called Bacillus Coagulans (which is one of the strains found in Threelac).