Antibiotics should not be used as a preventative, only for treatment.
Good bacteria as well as bad bacteria are killed off leaving bees (as well
as you and I for that matter) less resistant to disease. I personnally have
had
only one case of foulbrood in the last ten years. Many diseases show up
because bees have been weakened by mites. I noticed that the terramycin
made by Phizer no longer has instructions for use on bees.
 
H.Sweet