Potential of novel food-borne Lactobacillus isolates against the honeybee pathogen Paenibacillus larvae

An in vitro study was conducted to screen for the inhibitory potential of lactic acid bacteria (LAB), isolated from fermented food matrices, against the honeybee American Foulbrood agent Paenibacillus larvae. Various strains of Lactobacillus plantarum showed significant antagonism associated with their cell-free culture supernatant (CFS). The characterisation of this inhibition was based on assays and analyses involving different fraction and extracts. A significant effect was associated with media acidification resulting from LAB growth. However, this antimicrobial activity was found to be heat-stable and specific experiments suggested the implication of small antimicrobial peptides and/or antibiotics. Accordingly, a possible role of plantaricins released by L. plantarum in the culture supernatant was confirmed by the expression of different plantaricin-related genes. The results obtained in this study support further investigations on LAB strains as biological control agents for application in the apiary to preserve and improve honeybee health.