Susceptibility of the Honeybee Bacterial Pathogen Paenibacillus larvae to Essential Oils Distilled from Exotic and Indigenous Argentinean Plants.

Antimicrobial properties and chemical composition of eight exotic and indigenous Argentinean essential oils to control American Foulbrood (AFB) were determined. The oils tested were extracted from Artemisia absinthium, Artemisia annua, Lepechinia floribunda, Aloysia polystachya, Verbena officinalis, Wedelia glauca, Satureja odora and Hetherothalamus alienus. The components of the essential oils were identified by SPME-GC/MS analysis. The antimicrobial activity of the oils against Paenibacillus larvae were determined by broth microdilution method. Two-way ANOVA for minimum inhibitory concentrations (MICs) data and minimal bactericide concentrations (MBCs) data, indicated no significant differences between the thirteen P. larvae strains tested and highly significant differences between the oils. The antimicrobial assays showed that the oils of A. absinthium, A. annua and L. floribunda inhibited the bacterial strains at the lowest concentrations tested, MICs and MBCs averages of 393.6 mg/L to 416.7 mg/L and 517.9 mg/L to 624.4 mg/L respectively, indicating the highest inhibitory capacities. Their antimicrobial activities were attributed to the kind and the variation in percentage of the components. α-Thujone (62.3%) was largely predominant in the oil of the A. absinthium meanwhile artemisia ketone (36.3%) and 1,8-cineole (31.5%) constituted the bulk of the oil of A. annua. 1,8-Cineole (27.5%) was also very important in the composition of the oil of L. floribunda, which also possessed camphene (16.6%) and camphor (12.9%). [ABSTRACT FROM AUTHOR]