Sustainable biofilm control using lactic acid bacteria to disrupt quorum sensing in foodborne pathogens

Abstract

Biofilms formed by or entrapping foodborne pathogens pose a significant threat to food safety, as they confer increased resistance to sanitizers and contribute to persistent contamination. Quorum sensing (QS) is a bacterial communication mechanism regulating group behaviors based on population density. In particular, the autoinducer-2 (AI-2) QS enables intra- and interspecies interactions critical for biofilm development in various pathogens. Lactic acid bacteria (LAB), used in food fermentation for centuries, might disrupt QS in pathogens, offering an eco-friendly antibiofilm approach. This study assesses LAB-derived cell-free supernatants (CFSs) to interfere with AI-2-mediated QS and inhibit biofilm formation in Listeria monocytogenes and Staphylococcus aureus. Neutralized, sterile CFSs from 89 LAB isolates were initially screened for AI-2 QS interference via Vibrio harveyi luminescence assays. Twenty active CFSs were further tested at a sub-minimum inhibitory concentration (sub-MIC) for anti-biofilm effects using the conventional microtiter plate assay. The planktonic growth kinetics of the two pathogens exposed to these CFSs were also analyzed in parallel. Results showed that 61.8% of CFSs exhibited AI-2-like signals, while 28.1% significantly inhibited AI-2 QS. Most CFSs with interference reduced L. monocytogenes biofilm biomass, and one also decreased S. aureus by 45.4%. A specific antibiofilm action not accompanied by any reduction in the planktonic growth rate was evident in most cases. These findings suggest that LAB-derived metabolites target biofilm-specific mechanisms, with data indicating QS interference as a likely contributing factor, although direct evidence in the pathogens remains to be confirmed. Importantly, this approach does not impose selective pressure that might foster antimicrobial resistance. As natural, food-grade organisms, LAB might thus represent a sustainable alternative to synthetic biocides, aligning with environmentally responsible food safety strategies.