Hi all, I have been following this thread with interest. Here are some thoughts on the issue. First Nick is right oxytetracycline the antibiotic in terramycin (TM) does indeed break down rather quickly in the presence of warmth, moisture, or sunlight. This is the main reason that residues have not been found in honey from colonies with the drug in the hive during honey production. In the US the label for use in beehives requires that it be removed 4 weeks before the honeyflow as an added precaution. Some other drugs do not break down as quickly and therefore are much more likely to contaminate harvested honey. I suspect that it is the short life of active TM in the hive when it is administered as a dust with powdered sugar that has helped prevent the emergence of drug tolerant or resistant strains of Bacillus larvae in North America. If a beekeeper is using TM and finds a colony with AFB the colony should be destroyed as it could be drug resistant. It may not be but why take the risk. I agree with Allen that the widespread occurrence of such strains would have an impact on international trade in honey. Drug resistance appears when the drug selects for those few resistant members or the bacterial population by elimination their competition. The resistant stains become the dominate strains over time in the presence of the drug. These few resistant bacteria are already present in the population. The main factor in selecting for these resistant individuals is the presence of the drug in their environment for a long period of time ( in terms of generations of bacteria ). So if one wanted to develop resistant strains of a bacteria they would keep the drug present in an active state for a long time. About the only way of doing this with TM in a honey bee broodnest that I can think of is to protect the TM from moisture by mixing it with vegetable oil. My view is that TM is a valuable tool in cleaning up and dealing with AFB but we do need to use it wisely. All infected combs with scale should be destroyed by rendering, burning, or burying. TM is very helpful for cleaning up comb and equipment that has been exposed to AFB but does not contain scale. If you use TM and find AFB in a colony it is cheaper and simpler to just destroy the colony and therefore destroy a potential resistant strain that to try to clean it up. If other drugs are used, you are spreading the resistant strain. In other bacterial diseases, resistance to multiple drugs usually develops more quickly that resistance to the first drug so the use of alternate drugs may not buy much time. There are many things we as beekeepers can do to limit the spread of AFB and deal with it in our operations in addition to the use of TM. The main thing is to remember that any time you are moving broodcombs from one colony to another you may be moving scale. Many of our beekeeping brothers and sisters in other countries where they don't have the access we do to TM can give us in North America some ideas on how to deal with AFB economically without using TM and it would be good to hear from them. blane ****************************************** Blane White State Apiary Inspector Minnesota Department of Agriculture 90 W Plato Blvd St Paul, MN 55107 http://www.mda.state.mn.us phone 612-296-0591 fax 612-296-7386 [log in to unmask] ********************************************