Antimicrobial activity of essential oils against Paenibacillus larvae

GENDE LB; AFONSO PIRES SM; FERNANDEZ NJ; DAMIANI N,; CHURIO MS; FRITZ R; EGUARAS MJ

Lisboa

Congreso; International Symposium on Essential Oils; 2012

American foulbrood is a serious bacterial disease that affects Apis mellifera colonies; the causative agent is Paenibacillus larvae [1]. The aim of the study was to evaluate in vitro the antimicrobial activity of 32 essential oils against P. larvae. Oils from 21 botanical species were analyzed by gas chromatography (CG and CG/EM).  All essential oils were classified according to the composition of their main components in two groups: benzene ring compounds (BRC) and terpene compounds (TC). Minimal inhibitory concentration (MIC) in MYT broth [2] was assessed by the microdilution method. Final serial dilution concentrations of the essential oils ranged between 2,000-12.5 μg/mL. The bacterial isolates were collected from different Argentina’s region. The chromatographic analysis showed that a 67% of the essential oils contained predominately terpene compounds, while the remaining 33% included mainly compounds with benzene rings. From the TC group, Cymbopogon citratus essential oil showed the better antimicrobial activity against P. larvae with MIC values between 150 and 250 ug/ml. The essential oils from Aloysia polystachya and Mentha spp. had the lowest inhibitory activity. Among the oils from the BRC group, one of the lowest MIC values was found with cinnamon essential oil (Cinnamomun zeylanicum) being between 25 and 50 ug/ml; Origanum vulgare showed the highest MIC values (350-400 ug/ml). Essential oils, especially those with BRC in their composition, presented inhibitory capacity against P. larvae strains.