I found it unfortunately difficult to find a good bifido probiotic without acidophilus in it too. B. Infantus has good research involving IBS and inflammation. The particular strain involved in the research (because all strains are different) comes under the brand name Align. I can't take it because I'm allergic to cow's milk, and it has traces in it, but I've heard good things about it.
There are really only about 4 major types of Bifidobacteria you'll see around. B. Lactus may or may not be as good for some of us, since it produces a lot of lactic acid - some people seem to have too much, but on the other hand it's good for setting up a hospitable environment for other good bacteria. B. Infantus is a good one. But really, I imagine you'd do okay with any or all of the four if your levels are that low to begin with.
There are a lot of blends out there. I would choose the highest quality, most reputable manufacturer you can, if possible. The specific strains can matter quite a bit (e.g. one type of B. Bifidus and another type of B. Bifidus may have totally different effects, or one may have a ton of well-researched benefits and the other may not do much of anything). It's generally a good sign if the product lists the exact strain used (usually that involves some type of letter or number combination - e.g. B. Bifidus BB-06). Professional brands are often pretty safe since they have a high reputation to lose and are trusted by naturopaths and doctors - Pure Encapsulations, AOR, Douglas Labs, Metagenics, etc. They can be a bit harder to find and more expensive, but it seems to be worth the difference in many cases.
Also make sure to buy from a very trustworthy source when it comes to probiotics, since they're easy to kill through improper storage. It doesn't do you any good to save a few dollars on a bottle that's been sitting in some hot warehouse for too long and isn't actually alive anymore.
