Whoa!

 Terramycin does not kill EFB - it is a bacteriostat not a bacteriocide -
and
 will only stop EFB whilst the terramycin is active.  If the bees do not
 clear the bacteria during this temporary break, then EFB will recur.

 Yellow larvae may be due to their diet - a yellow gut, from eating pollen,
 is a good sign; EFB bacteria multiplying in the gut cause it to turn white
 and this is a classic sign of EFB.  The obvious symptoms are dying
 (unsealed) larvae with a melted down appearance and larvae that move into
 unnatural positions, typically twisting and turning over so that their
backs
 are facing the top of the cell.

 See:
 http://www.csl.gov.uk/prodserv/cons/bee/factsheets/fbleaflet.pdf
 for full details.

 Peter Edwards