In-vitro Evaluation of the Antibacterial Activity of Micromeria barbata Essential Oil Against Paenibacillus larvae Spores, Causative Agent of AFB

Abstract

Paenibacillus larvae are the causative agent of American foulbrood, 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. Residues of antibiotics in honeybee products make them harmful and unsafe if consumed by humans, especially pregnant women and infants, until the age of eight. Using a natural product, such as plant essential oils, instead of synthetic antibiotics may aid in treating such diseases. In this study, the antibacterial activity of Micromeria barbata ssential oil was investigated against both forms of Paenibacillus larvae and the toxic effect of this essential oil on honeybees was also tested. The broth dilution method of the tested essential oil was used to determine the MIC of the oil against the vegetative form Paenibacillus larvae and two other methods were used for the spore form Paenibcillus larvae. The acute toxicity of Micromeria barbata essential was tested using different routes of administration. The results 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 one. Spraying and feeding the essential oil appeared safe and not toxic to honeybees. in summary, our findings indicate that the tested essential oil can be used as a natural alternative to synthetic antibiotics in treating American foulbrood disease.