Control of oxytetracycline-resistant American foulbrood with tylosin and its toxicity to honey bees (Apis mellifera)

The antibiotic tylosin was found to be effective in controlling oxytetracycline-resistant American foulbrood (Paenibacillus larvae) in honey bee (Apis mellifera) colonies, while not affecting adult and larval honey bee mortality. An optimal rate of 200 mg tylosin, applied in 20 g of confectioners' sugar at weekly intervals for three weeks resulted in complete remission of detectable disease symptoms 45 days after initial treatment. No detectable disease symptoms were observed seven months after treatment with this rate. Various higher doses of tylosin (600 mg and 1000 mg per 20 g confectioners' sugar) applied over three honey bee brood cycles, resulted in no significant increase in adult and larval bee mortality when compared with controls. Discussion is given as to long term American foulbrood control and tactics for resistance management.