It is my understanding, having not read the label myself(anybody have one?) that it (the label) reads "for the cure of AFB". Discussions here with other beekeepers, regulators and extension persons, this means that once you find AFB in your apiary that you should follow state regs on AFB(ie. burn the infected colony) and treat the others with tylosin.
NOT MY RECOMMENDATION.
Seems to me that if you have taken care of the infected colony then you shouldn't automatically treat the others.
I also understand that tylosin doesn't "break down" as fast as terramycin, so if you use it, be careful when and perhaps, to be safe, remove all honey supers.
Mark Berninghausen "To float, upheld, as salt water would hold you, once you dared." Denise Levertov, poet