New approaches for the control of Campylobacter jejuni biofilms in the food industry are being studied intensively. Natural products are promising alternative antimicrobial substances to control biofilm production, with particular emphasis on plant extracts. Dried flowers of Lavandula angustifolia were used to produce essential oil (LEO), an ethanol extract (LEF), and an ethanol extract of Lavandula postdistillation waste material (LEW). The chemical compositions determined for these Lavandula preparations included seven major compounds that were selected for further testing. These were tested against C. jejuni for biofilm degradation and removal. Next-generation sequencing was used to study the molecular mechanisms underlying LEO actions against C. jejuni adhesion and motility. Analysis of LEO revealed 1,8-cineol, linalool, and linalyl acetate as the main components. For LEF and LEW, the main components were phenolic acid glycosides, with flavonoids rarely present. The MICs of the Lavandula preparations and pure compounds against C. jejuni ranged from 0.2 mg/ml to 1 mg/ml. LEO showed the strongest biofilm degradation. The reduction of C. jejuni adhesion was ≥1 log10 CFU/ml, which satisfies European Food Safety Authority recommendations. Lavandula preparations reduced C. jejuni motility by almost 50%, which consequently can impact biofilm formation. These data are in line with the transcriptome analysis of C. jejuni, which indicated that LEO downregulated genes important for biofilm formation. LEW also showed good antibacterial and antibiofilm effects, particularly against adhesion and motility mechanisms. This defines an innovative approach using alternative strategies and novel targets to combat bacterial biofilm formation and, hence, the potential to develop new effective agents with biofilm-degrading activities. IMPORTANCE The Lavandula preparations used in this study are found to be effective against C. jejuni, a common foodborne pathogen. They show antibiofilm properties at subinhibitory concentrations in terms of promoting biofilm degradation and inhibiting cell adhesion and motility, which are involved in the initial steps of biofilm formation. These results are confirmed by transcriptome analysis, which highlights the effect of Lavandula essential oil on C. jejuni biofilm properties. We show that the waste material from the hydrodistillation of Lavandula has particular antibiofilm effects, suggesting that it has potential for reuse for industrial purposes. This study highlights the need for efforts directed toward such innovative approaches and alternative strategies against biofilm formation and maintenance by developing new naturally derived agents with antibiofilm activities.
Keywords: Campylobacter jejuni; Lavandula preparations; antibiofilm activity.