I always look for peer-reviewed studies - and more than one - but there are precious few that I trust. And of course, the studies do not reveal where they source their cultures because they cannot be seen to promote a given supplier. However, since I used to attend a number of CF conferences for my work, I did buttonhole one researcher who admitted they got their L. acidophilus from Culturelle. This was years ago, but I still use that one. It worked great for IV antibiotic-induced diarrhea, but now I'm searching for probiotics to help treat SIBO, so I'm going to have to try to contact some of my old (and I do mean old) colleagues.
Please note I am not promoting Culturelle. The company may have changed hands 10 times since then for all I know. Also, YMMV!