Here is a link to an article about how probiotics reduced levels of American Foulbrood infections. However, before you go buy some consider the following.
1) Standard practice is to KILL and BURN hives with American Foulbrood (AF). Since the probiotic did not eradiate the AF you may still need to KILL and burn your hive.
2) In 10 years I have only heard of one (1) case of AF among all ECWBA members and in only in one hive. The state inspector required this hive be killed and burned. I don't believe this alternate approach is approved for use in treating AF.
3) Before you go to expense of using probiotics prophylactically you should consider the expense of the probiotics and the small probability of catching AF. In other words you should do a cost benefit calculation.
4) The study said probiotics "significantly" increased hive survival. The value of the term "significantly" was not defined.