A new study published in MDPI Foods demonstrated the antimicrobial efficacy of select essential oils against multidrug-resistant (MDR) Campylobacter, potentially offering an effective natural control strategy in food production.

The study’s researchers obtained seven commercially available essential oils—Cymbopogon citratus, Mentha pulegium, Artemisia absinthium, Myrtus communis, Thymus algeriensis, Thymus capitatus, and Eucalyptus globulus—and tested them against MDR C. coli and C. jejuni strains isolated from poultry in Tunisia. The most effective essential oils were further evaluated through time–kill kinetics, cell lysis, salt tolerance, and membrane integrity assays to determine their bactericidal mechanisms.

Efficacy Varied by Strain, Oil Type

A broth microdilution assay showed that oils from E. globulus, T. algeriensis, and M. communis exhibited the strongest inhibitory effects, particularly against C. jejuni, with minimum inhibitory concentration (MIC) values ranging from 3.125 percent to 6.25 percent. On the other hand, C. coli was more resistant to all essential oils. The higher resistance of C. coli underscores the importance of considering species-specific responses when designing essential oil-based antimicrobial interventions.

T. capitatus, A. absinthium, and M. pulegium also demonstrated measurable antibacterial activity, although to a lesser extent, highlighting variability in essential oil potency and species-specific susceptibility.

Interestingly, in a disk diffusion assay, T. algeriensis demonstrated comparable inhibitory effects against both C. coli and C. jejuni, indicating a broad antibacterial spectrum. This finding could have potential implications regarding the development of essential oil-based interventions intended to control multiple Campylobacter strains in food production.

Oils Work Against Microbes by Damaging Cell Membranes

Mechanistic investigations revealed that the antibacterial action of these essential oils is primarily membrane-targeted. The rapid bactericidal effects observed in time–kill assays, together with significant cell lysis, cytoplasmic material leakage, and impaired salt tolerance, indicate severe disruption of cell membrane integrity and loss of osmotic homeostasis. These findings provide strong evidence that essential oils act mainly through physical damage to bacterial membranes rather than solely through metabolic inhibition.

Importantly, the ability of essential oils to disrupt stress adaptation mechanisms, such as tolerance to elevated sodium chloride concentrations, suggests an additional mode of action that could reduce Campylobacter survival in food production environments.

Organoleptic Considerations

The researchers note, however, that the essential oil concentrations required for antimicrobial efficacy may exceed sensory acceptance thresholds in certain food matrices, potentially limiting their direct application due to strong organoleptic effects.

Future research could explore delivery systems such as micro- or nanoencapsulation, incorporation into edible coatings or active packaging, and integration within hurdle technology approaches.