A potential role of tannins in the control of American foulbrood

Aim of study: To evaluate the use of tannins extracts in the control of the American foulbrood pathology and to investigate if these extracts present levels of toxicity on Apis mellifera. Area of study: Paenibacillus larvae strains C1 and C2 were from Balcarce, province of Buenos Aires, strain C6 from Rio Cuarto, in Cordoba province and strain C9 from Concordia in Entre Rios province. Bees larvae used for toxicological assays were collected in Santa Paula experimental apiary, Mar del Plata (belonging to the Centro de Investigacion en Abejas Sociales (CIAS-IIPROSAM) from UNMdP. Material and methods: The minimal inhibitory concentration (MIC) of five different tannin extracts were obtained by agar diffusion method on four P. larvae strains; using the MIC value, the toxicity test on A. mellifera larvae was performed afterwards. Main results: The MIC value was in the range of 6.9 to 898.6 mu g/mL. Three tannin extracts did not show toxicity against bee larvae; however, those that were fed with the latter showed a significant increase in weight. Research highlights: Three tannins extracts showed a good antimicrobial activity against P. larvae and they did not show toxicity against bee larvae.