Researchers Propose Listeria Biofilm Colonization Hypothesis to Explain Persistence in Food Processing Plants
A new mini-review published in the Journal of Food Protection has proposed a novel ecological explanation for why Listeria monocytogenes can persist in food processing environments despite routine sanitation. Rather than competing directly with established microbial communities, the authors hypothesized that the pathogen acts as a "secondary colonizer," exploiting nutrient-rich voids left behind when Gram-negative biofilms naturally disperse.
Novel ‘Secondary Colonizer Hypothesis’
The proposed "Secondary Colonizer Hypothesis" suggests that L. monocytogenes colonizes the vacant spaces created during biofilm dispersal, where low oxygen conditions and cellular debris provide favorable conditions for growth. According to the authors, the pathogen may capitalize on specialized metabolic pathways that enable it to utilize ethanolamine, propylene glycol, and glycerol while reducing ferric iron for respiration, potentially giving it a competitive advantage in these microenvironments.
Veillonella as a Key Bridging Species
The review also highlighted evidence suggesting that Veillonella species may play an important role in this ecological succession. Previous statistical analyses and more recent laboratory studies have associated Veillonella with L. monocytogenes in food processing environments and demonstrated that metabolites produced by Veillonella can enhance L. monocytogenes growth under both planktonic and biofilm conditions. The authors suggested these findings support the biological plausibility of the proposed colonization model, although they noted that further validation is needed.
Shifting Food Safety Programs to Consider Biofilm Ecology
Based on the hypothesis, the authors argued that food safety programs could benefit from placing greater emphasis on managing biofilm ecology rather than focusing exclusively on pathogen detection. They suggested that environmental monitoring could incorporate surveillance of Gram-negative biofilm formation, dispersal events, and potential indicator organisms such as Veillonella. The review also discussed the possible importance of minimizing residues of compounds including ethanolamine, propylene glycol, and glycerol in no-rinse sanitation applications, as well as maintaining equipment to reduce rust and iron availability in critical hygiene zones.
Validation and Future Research Needs
The authors emphasized that the Secondary Colonizer Hypothesis remains a conceptual framework that requires experimental validation under industrial conditions. They called for future research to investigate the timing of biofilm succession, characterize the physicochemical conditions that favor secondary colonization, and evaluate intervention strategies that disrupt ecological succession without promoting antimicrobial resistance.
Sanitation Industry-Commissioned Research
Published in the Journal of Food Protection, the research was commissioned by Diversey, a cleaning and hygiene solutions provider, and was led by Jack Burnett, Ph.D., associated with Purdue University, and Dale Grinstead, Ph.D., an industrial microbiologist and founder of Mountain Top Microbiology, an independent consultancy.
Looking for quick answers on food safety topics?
Try Ask FSM, our new smart AI search tool.
Ask FSM →
