Based upon my experience resistant AFB is fairly rare; in my area most
cases can be traced back to one original beekeeper who sold hives to
the others.

My theory is that resistant AFB is developed in colonies with long
term infections in the presence of terramycin; either patties, syrup,
or perhaps residual terramycin left from years of over-use.

 I do not see how a hive that never gets foulbrood due to preventative
use of terramycin, could then develop resistant bacteria. The spores
cannot develop anything in the spore stage.  I am not sure if anyone
has really figured this one out.

Of course, you can get it from someone else, as I have suggested. By
the way, it appears that tylosin can clear up EFB though it is not
labeled for this use. Again, I would avoid tylosin unless you really
need it, because it does build up in the hives.

pb

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