[...unfortunately the only one specifically mentioned.]
Seems MAN reads one article and implies he has to tinker with it to make things BETTER. But nature is a BALANCE that man's feeble mind tends to not completely comprehend.
MAN tries to make everything fit his understanding instead of being how it actually is.
Even within this conversation, MAN is trying to force an improvement on digestion and infection with the ASSUMPTION that the digestive systems work the same for bees as it does in man.
While we need bacteria to complete digestion of some food, the same is not true for bees. While some bacteria may hold beneficial properties by holding down some infections, more is not always better. In fact, while the bacteria maybe beneficial, it does not imply it is NECESSARY for their survival.
The treatment of pollen with lacto-bacillus isn't for digestive improvement, but for long term storage. Fortunately, certain enzymes arise from the process that do greatly improve honeybee health.
The best proactive natural defense you can provide your bees is making adequate quality forage available as much of the year as possible. In doing so, the bees limited immune system will cleanse much of the disease on its own. Good nutrition results in the fastest healing from disease or injury.
The second necessary thing is as BuckBee said, keeping good husbandry practices like avoiding excessive cold, dampness, or draft (all issues of stress that compromise the immune system). Includes with keeping a quality environment is protection from parasites such as mites and beetles.
Bees depend on YOU for their placement because YOU take that choice away from them by placing them where YOU want them. That's a lot of responsibility.
Along with BuckBee's comment and my rant about human placement of colonies, is the matter of house keeping. By buying or capturing bees and putting them in boxes of YOUR choice, you have to be sure that you are providing a healthy home. I find very few people that know what it takes to properly sanitize equipment. Not every disease requires the same method, and no one method is universal for every disease (though a few come close).
Read, study, observe and let nature do its thing.
Intervene where you have created the responsibility to react.
Stop assuming the bees need more chemicals from you to survive.
I do not blindly comment on these issues.
I too once did not understand and violated these conditions and suffered the consequences.
But you too can learn and advance yourself into being a better beekeeper.
Your bees will greatly appreciate it.
There is always more than one way to skin a cat, that's of course if you're into eating cats.