Inhibition of Single and Mixed Species Biofilms Formed by Listeria monocytogenes and Food Related Bacteria by Natural Compounds

Abstract

Pathogenic bacteria, such as Listeria monocytogenes, are easily transferred from biofilms on processing equipment to foods, causing many foodborne outbreaks and illnesses. The antimicrobial and anti-biofilm effects of natural compounds, thymol, carvacrol, trans-cinnamaldehyde and lemongrass essential oil were tested against single and mixed species biofilms of Listeria monocytogenes, Salmonella enterica Typhimurium, Staphylococcus aureus, Pseudomonas fluorescens and Shewanella baltica. All natural antimicrobials inhibited single and mixed species biofilm formation and planktonic growth, however, biofilm removal depended on bacteria, antimicrobial, maturity of the biofilm and mixed species interactions. Generally, biofilm cells showed higher resistance than planktonic cells. Bacterial survival in mixed species mostly decreased compared to single species biofilm. Bacterial proportions in mixed species biofilm were modulated by the bacterial species and treatment compound. These results support use of natural antimicrobial compounds to target biofilms formed by pathogenic and spoilage bacteria to improve the hygiene and food safety in food processing environments.