Well, from what I've read, Bacteroides is beneficial to the gut but if you have a leaky gut and it gets out of the gut it can cause problems. It's read that this potential danger is why most commercial manufacturers have shied away from it. In my case the beneficial effect is so pronounced that it's worth trying despite the possible risk, and also my vulnerability that led to the candida seems to be limited to the gut; I'm pretty sure my immune system is normal over the rest of my body. So from what I've read, it doesn't sound like I would be at significant risk of it spreading.
Also, the species of Bacteroides which is known to cause infection is B. fragilis. The strain used in Prescript-assist is B. liplyticum. As an analogous example, E. coli is widely known to cause infection but the strain E. coli Nissle 1917 has actually been used for decades as a probiotic for ulcerative colitis. You can't generalize from one strain or species of bacteria to the entire genus. That would be like saying that because pit bulls are dangerous, so are poodles.
Lastly, I read the reviews for Prescript-Assist on Amazon from dozens of people and none of them reported bad side effects, even after months of use. I also checked on Google and couldn't find any reports of negative side effects.
So for me personally, the benefits outweigh the risks. But it's going to be different for every person. If you're immunocompromised or pretty sure you have a leaky gut, I wouldn't recommend taking it. You have to weigh the benefits and the risks given your own condition.