Allen asked for some studies.  I found one:
J Invertebr Pathol. 2003 May;83(1):46-50.

Diverse origins of tetracycline resistance in the honey bee bacterial
pathogen Paenibacillus larvae.

Evans JD.

USDA-ARS Bee Research Laboratory, BARC-East Bldg. 476, Beltsville, MD 20705,
USA. [log in to unmask]

Abstract

Paenibacillus larvae is the causative agent of the important honey bee
larval disease American Foulbrood (AFB). This pathogen has been treated in
bee colonies by a single registered antibiotic, oxytetracycline (OTC), for
fifty years. Recently, widespread resistance to OTC has been reported. In
this study, the degree of antibiotic resistance was contrasted with DNA
sequence variation for 125 P. larvae isolates collected in North America.
Resistance was uncorrelated with bacterial haplotype, suggesting either that
resistance has evolved multiple times in P. larvae or that resistance
involves recent horizontal transfer via a non-genomic (e.g., plasmid or
conjugal transposon) route. The recency of OTC resistance in P. larvae
across this broad survey area underscores the need to manage foulbrood
infections carefully and to monitor populations for resistance.

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