In-vitro Evaluation of the Antibacterial Activity of Micromeria barbata Essential Oil Against the bacteria Paenibacillus larva, the Causal Agent of American Foulbrood Disease of Honeybee

Abstract

Paenibacillus larvae is the bacterial causal agent of the American foulbrood (AFB), one of the most widespread and destructive honey bee brood diseases. The misuse and overuse of antibiotics in treating AFB can potentially promote antibiotic resistance and the residues of the antibiotics used may be found in honeybee products, which makes them harmful and unsafe if consumed by humans, especially pregnant women and infants, until the age of eight. Using natural products, such as plant essential oils, instead of synthetic antibiotics may aid in treating such diseases. In this study, the antibacterial activity of Micromeria barbata essential oil was investigated against both forms of Paenibacillus larvae. In addition, the toxic effect of this essential oil on honeybees was also investigated, using feeding and spray methods of the tested essential oil, to determine the minimum inhibitory concentration (MIC) of the oil against the pathogen Paenibacillus larvae. The acute toxicity of Micromeria barbata essential oil was tested using different routes of administration. The results obtained showed a difference in the action of the essential oil between the two forms of the tested bacteria. The tested essential oil appeared to be bactericidal against the vegetative form of the tested bacteria and sporicidal against the spore form. Spraying and feeding the essential oil appeared safe and non-toxic to honeybees. It can be concluded from this study that the tested essential oil can be used as a natural alternative to synthetic antibiotics in treating American foulbrood disease.

Keywords:

Essential oils, Micromeria barbata, antibacterial action, toxicity, American foulbrood disease, Paenibacillus larvae, honeybee.