Control of Growth and Persistence of Listeria monocytogenes and β-Lactam-Resistant Escherichia coli by Thymol in Food Processing Settings

Abstract

The main objective of this study was to evaluate the efficacy of thymol in controlling environmental contamination in food processing facilities. The effect of thymol was tested as an agent to prevent planktonic and bacterial biofilm growth of twenty-five Listeria monocytogenes isolates from a variety of foods and five Escherichia coli isolates from a farm. The E. coli isolates were positive for extended spectrum β-lactamase (ESBL) genes. All isolates and reference strains were susceptible to thymol at Minimum inhibitory concentration (MIC) values ranging from 250 to 800 μg/mL. An interesting activity of interference with biofilm formation of L. monocytogenes and E. coli was found for thymol at sub-MIC concentrations of 200, 100, 75, and 50 μg/mL. Anti-biofilm activity ranging from 59.71% to 66.90% against pre-formed 24-h-old L. monocytogenes biofilms at concentrations of 500 or 800 µg/mL, corresponding to 2× MIC, was determined against free-living forms of six isolates chosen as the best or moderate biofilm producers among the tested strains. The property of thymol to attack L. monocytogenes biofilm formation was also observed at a concentration of 100 µg/mL, corresponding to 1/4 MIC, by using a stainless-steel model to simulate the surfaces in food industries. This study gives information on the use of thymol in food processing setting.

Investigating Transcriptomic Induction of Resistance and/or Virulence in Listeria monocytogenes Cells Surviving Sublethal Antimicrobial Exposure

“…The MIC of AMP against both bacterial strains was found equal to 0.125 µg/mL. This is a value similar to those described in the literature for that antibiotic and bacterial species [53,65]. Similarly, the MICs of BAC and THY previously determined equal to 2 and 78.1 µg/mL, respectively, against both strains [39], were similar to the ones previously reported for those compounds against that pathogenic species [56,66].…”

“…All the antimicrobials applied here were previously verified for their strong killing efficiency against L. monocytogenes cells, as well as many other detrimental microorganisms [36,53,54]. Nevertheless, foodborne L. monocytogenes isolates displaying resistance to BAC [55,56] and enough times in parallel to other drugs, such as antibiotics and some other toxic compounds, have also been described [57,58].…”

Shift of Volatile Organic Compounds (VOCs) in Gluten-Free Hemp-Enriched Sourdough Bread: A Metabolomic Approach

“…[23,[25][26][27] thymol herbal, thyme, phenolic, medicinal, camphor contrast spoilage microorganism bacterial foodborne and entero-pathogens; anti-inflammatory and antioxidant in human preadipocytes and in neuroprotection of rotenone-induced rat model of Parkinson's disease. [28][29][30][31] terpineol pine, terpene, lilac, citrus, woody, floral contrast spoilage microorganism bacterial foodborne and entero-pathogens; anti-inflammatory and antioxidant in LPS-induced cell line.…”

“…1-octen-3-ol derives from linoleic acid during oxidative breakdown, and it has antimicrobial activity against spoilage and opportunistic microbes [24]. Borneol, thymol, and terpineol are considered bioactive molecules and are reported to modulate beneficially the gut microbiome [25,28,32] and to possess anti-inflammatory and antioxidant activity [26,29,30,33]. Their exclusive presence in HSF products can be considered an added value, particularly because they were retained in HSF breads, with borneol as the most resistant (43% retained).…”

Advanced Killing Potential of Thymol against a Time and Temperature Optimized Attached Listeria monocytogenes Population in Lettuce Broth

“…One of the well-studied plant antimicrobial compounds is thymol (THY), which is the main component of the essential oils (EOs) of thyme, oregano, and some other widely distributed plants in the Mediterranean region [ 19 ]. However, although several studies have been occupied with the anti-biofilm action of THY against many microorganisms, including L. monocytogenes [ 20 , 21 , 22 , 23 , 24 ], little is still known on the superiority (if any) of that compound or other phytochemicals over some other classical surface disinfectants [ 25 , 26 , 27 ]. Considering all the above, the main aim of the current study was to compare the effectiveness of THY to that of benzalkonium chloride (BAC), a well-known quaternary ammonium compound (QAC) widely used as biocide in many sanitizing formulations applied in industrial, health care, home, and cosmetics settings [ 28 ], against sessile L. monocytogenes bacteria under attachment conditions trying to simulate as much as possible those encountered in the salad industry.…”