Antimicrobial activity of phenolic extract of apple pomace against Paenibacillus larvae and its toxicity on Apis mellifera

GIMENEZ MARTINEZ PABLO; RAMIREZ AMBROSI, M; FUENTES GISELL; QUINTANA, SILVINA

Congreso; EurBee 8. 8th Congress of Apidology; 2018

Eurbee

Apis mellifera populations are threatened by different biotic and abiotic stressors that affect the bee survival. Pathogens and parasites are among the most important factors that cause mortality of bees. Paenibacillus larvae, the causative agent of American foulbrood, is one of the most important bacterial pathogens that affect bee health. The use of antibiotics, particularly tetracycline hydrochloride (OTC), is the most common method for prevention and treatment of infected colonies. The extended use of synthetic drugs is known to generate several problems, including the presence of chemical residues in the beehive products (honey, pollen and wax), which eventually may even affect consumer health. However this application can increase the risk of occurrence of resistant strains. An ecological alternative is the use of vegetal extracts containing bioactive compounds, such as polyphenols. The aim of the present study was to evaluate the antimicrobial activity of phenolic extracts of apple pomace, coming from the cider industry, against P. larvae by the broth microdilution method. Besides, the toxicity of the extracts on A. mellifera was evaluated using the complete exposure method. All extracts contemning from 1022 to 9364 mg/g of total phenolic contents, determined by HPLC-DAD, showed antimicrobial activity against P. larvae genotype ERIC I, ranging from 20 µgmL-1 to 150 µgmL-1.Toxicity assays of apple pomace extracts on adult bees exhibited a maximum mortality of 18% after 48h. Although some extracts analyzed in the present study showed higher MIC values than OTC, apple pomace extracts are still promising, since being natural products they would lack the problems that synthetic antibiotics have, including the presence of residues in the behive products and the occurrence of resistant strains. Furthermore the reuse of agroindustrial residues such as apple pomace that are generated in great quantity causing environmental problems, is being paid attention by governments and environmental protection institutions.