Inhibitory Effect of Essential Oil and Oleoresin of Clove (Syzygium aromaticum) on Food-Borne Escherichia coli and Salmonella spp.

Background: Foodborne pathogens, particularly Escherichia coli and Salmonella spp., present significant health risks, exacerbated by the growing resistance to antibiotics. This study explores the potential of clove ( Syzygium aromaticum ) essential oil and oleoresin as natural antimicrobial agents against these pathogens. Methods: Essential oil and oleoresin were analyzed using gas chromatography-mass spectrometry, revealing eugenol, eugenyl acetate, and caryophyllene as the dominant compounds. Results: Antibacterial efficacy was assessed using minimum inhibitory concentration and minimum bactericidal concentration assays, showing clove essential oil to be more potent than oleoresin. The inhibitory effects were further confirmed through time-kill analysis, where clove essential oils exhibited potent bactericidal effects, whereas oleoresins demonstrated bacteriostatic activity. Morphological changes in E. coli and Salmonella spp., including elongated cell forms, suggested a disruption in cell division. Clove essential oil also effectively inhibited biofilm formation by up to 80%, compared to 60% by oleoresins. When applied to artificially contaminated food matrices (chicken and prawns), clove essential oil demonstrated up to a 2-log reduction in Salmonella spp. and a 1-log reduction in E. coli colony counts. Moreover, the essential oil influenced virulence gene expression in both pathogens, indicating its ability to suppress bacterial pathogenicity. Conclusion: The findings suggest that clove essential oil, with its potent antimicrobial properties, could be an effective natural preservative, offering a safer alternative to synthetic agents in food safety applications.