Antimicrobial and Antibiofilm Potential of Thymus vulgaris and Cymbopogon flexuosus Essential Oils against Pure and Mixed Cultures of Foodborne Bacteria

Abstract

The spread of pathogenic and food spoilage microorganisms through the food chain still faces major mitigation challenges, despite modern advances. Although multiple cleaning and disinfection procedures are available for microbial load reduction in food-related settings, microbes can still remain on surfaces, equipment, or machinery, especially if they have the ability to form biofilms. The present study assessed the biofilm-forming properties of pure and mixed cultures of foodborne and spoilage bacteria (Listeria monocytogenes, Enterococcus faecalis, Aeromonas hydrophila, Brochothrix thermosphacta), using polystyrene and stainless steel contact surfaces. Subsequently, the antimicrobial and antibiofilm properties of Thymus vulgaris and Cymbopogon flexuosus essential oils—EOs—were evaluated against these bacteria. Moreover, in silico prediction of the absorption and toxicity values of the EOs’ major constituents was also performed, perceiving the putative application in food-related settings. Overall, biofilm formation was observed for all microbes under study, at different temperatures and both contact surfaces. In polystyrene, at 25 °C, when comparing pure with mixed cultures, the combination Listeria–Aeromonas achieved the highest biofilm biomass. Moreover, at 4 °C, increased biofilm formation was detected in stainless steel. Regarding thyme, this EO showed promising antimicrobial features (especially against A. hydrophila, with a MIC of 0.60 µg/µL) and antibiofilm abilities (MBEC of 110.79 µg/µL against L. monocytogenes, a major concern in food settings). As for lemongrass EO, the highest antimicrobial activity, with a MIC of 0.49 µg/µL, was also observed against L. monocytogenes. Overall, despite promising results, the in situ effectiveness of these essential oils, alone or in combination with other antimicrobial compounds, should be further explored.

Tetraclinis articulata (Vahl) Mast.: Volatile constituents, antioxidant, antidiabetic and wound healing activities of its essential oil

“…The observed anti-biofilm activity of TAEO against these target bacteria could be potentially attributed to the permeation capacity of oxygenated monoterpenes (38.83 %) to disrupt crucial stages in the biofilm formation process, including the production of adhesion proteins and the disruption of the exopolysaccharide matrix (EPS) of the bacterial biofilm [ 70 ]. Previous studies have attributed similar antibiofilm effects to the significant presence of oxygenated monoterpenes in essential oils, such as those derived from Backhousia citriodora [ 71 ], Thymus vulgaris L. [ 72 ], and Cymbopogon flexuosus [ 73 ].…”

The Prevalence, Isolation, and Antimicrobial Susceptibility Testing of Enterococcus Species From Various Clinical Samples in a Tertiary Care Hospital

“…Enterococcus is routinely considered a low-grade pathogen. The capability of Enterococcus species to survive in a range of unfavorable environments permits numerous paths of cross-contamination of Enterococci in human disease (Zaheer et al, 2020), combining those from food, environmental (Ferguson et al, 2013;Kim et al, 2022;Monteiro et al 2023), and hospital sources (Kwit et al, 2023;Ramos et al, 2020). The bacteria have come into view as an expanding and significant cause of nosocomial infection in recent decades (Hufnagel et al, 2004;Spengler et al, 2009.;Yadav et al, 2017).…”