Non-conventional molecules to control of Paenibacillus larvae, causal agent of American foulbrood

CUGNATA, N. M.; PELLEGRINI, M. C.; GUASPARI, E.; ALONSO SALCES, ROSA MARIA; FUSELLI, S. R.

Murcia

Conferencia; 6th European Conference of Apidology EURBEE; 2014

Universidad de Murcia y el Campus de Excelencia Internacional 'Mare Nostrum 37/38'

American foulbrood (AFB) is a serious disease that affects the larvae of honeybee Apis mellifera. It is caused by Paenibacillus larvae, a resistant spore forming bacterium, which remains viable through long periods of time and survives environmental adversities. This plague is usually controlled with antibiotics which could leave toxic residues in honey and by-products. Laboratory and field trials were conducted to evaluate the effectiveness of non-conventional molecules in the prevention and control of AFB in honeybee colonies. Twelve compounds were screened in order to test their antimicrobial activity against P. larvae. Lauric acid and menadione, an innocuous saturated fatty acid and a liposoluble vitamin, were selected to continue the study. The antimicrobial activity of the molecules against ten P. larvae strains was determined by the broth microdilution method. Lauric acid minimal inhibitory concentration (MIC) mean value was 20.31 mg mL-1 and the MIC menadione mean value was 2.145 μg mL-1. Toxicity to adult honeybees was tested by the complete exposure method. Non mortality was registered when using quantities up to 440 μg and 1500 μg of menadione and lauric acid, respectively. The results obtained in the present study contribute to the knowledge of the use of alternative natural compounds to control AFB in the apiaries. This way, toxicological risks and other undesirable effects, such as resistance due to the indiscriminate use of antibiotics, would be avoided.