Traces of contamination-well preserved in honey: investigation of veterinary drugs and American foulbrood in honeys of global origin.
In our study, honey samples of different global and local origins were tested for antibiotic residues as well as the presence of the bacterium Paenibacillus larvae, the causative agent of the honeybee disease American foulbrood (AFB). 30 German and 47 imported non-European honeys were analyzed for sulfonamides, trimethoprim, tetracyclines, macrolides, lincomycin and chloramphenicol. 22 of the imported honeys contained residues (in most cases more than one), whereas 29 of the 30 German samples were free of residues. Sulfamethoxazole was the most frequently found antibiotic (often combined with trimethoprim). Almost all of the analyzed honeys from Argentina, China and Canada were AFB-positive (category I and II), whereas only five German honeys were AFB-positive. A correlation of present antibiotics and AFB spores was not found. For investigating putative relations between imported honeys and AFB cases in the area of Hamburg, genomic fingerprinting by PCR-amplification of repetitive DNA elements of the bacterial isolates was performed. The study shows that distinct genotypes of P. larvae are prevalent in samples of different geographical origin. AFB isolates of imported honeys differ from the predominant genotype in the area of Hamburg. Furthermore, the prevalent genotype in Hamburg was characterized by the absence of the iC9-fragment which was shown to be linked to virulence of P. larvae strains.