Antibiofilm effect of plant derived antimicrobials on Listeria monocytogenes

Abhinav Upadhyay, Indu Upadhyaya, Anup Kollanoor-Johny, Kumar Venkitanarayanan

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The present study investigated the efficacy of sub-inhibitory concentrations (SICs, concentrations not inhibiting bacterial growth) and bactericidal concentrations (MBCs) of four, generally recognized as safe (GRAS), plant-derived antimicrobials (PDAs) in inhibiting Listeria monocytogenes (LM) biofilm formation and inactivating mature LM biofilms, at 37, 25 and 4°C on polystyrene plates and stainless-steel coupons. In addition, the effect of SICs of PDAs on the expression of LM genes critical for biofilm synthesis was determined by real-time quantitative PCR. The PDAs and their SICs used for inhibition of biofilm were trans-cinnamaldehyde (TC 0.50, 0.75mM), carvacrol (CR 0.50, 0.65mM), thymol (TY 0.33, 0.50mM), and eugenol (EG 1.8, 2.5mM), whereas the PDA concentrations used for inactivating mature biofilms were 5.0 and 10.0mM (TC, CR), 3.3 and 5.0mM (TY), 18.5 and 25.0mM (EG). All PDAs inhibited biofilm synthesis and inactivated fully formed LM biofilms on both matrices at three temperatures tested (P<0.05). Real-time quantitative PCR data revealed that all PDAs down-regulated critical LM biofilm-associated genes (P<0.05). Results suggest that TC, CR, TY, and EG could potentially be used to control LM biofilms in food processing environments, although further studies under commercial settings are necessary.

Original languageEnglish (US)
Pages (from-to)79-89
Number of pages11
JournalFood Microbiology
Issue number1
StatePublished - Oct 2013


  • Biofilms
  • Gene expression
  • Listeria monocytogenes
  • Plant derived antimicrobials


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