The Paradox of Mixed-Species Biofilms in the Context of Food Safety

Formation of mixed-species biofilms constitutes a common adaptation of foodborne pathogens and indigenous microbiota for prolonged survival in their food niche. Nevertheless, the potential role of mixed-species biofilms in food safety remains to be elucidated. The formation of mixed-species biofilms on food and food processing surfaces depends on various physical, chemical, and biological processes including species composition, especially of the indigenous microbiota and nutrients, food types, temperature, quorum sensing, extracellular polymeric substance (EPS) production, biofilms maturation, and dispersal steps. Compared to monospecies, mixed-species are highly resistant to antimicrobials, possibly due to higher EPS production, internalization into food, fitness of species, denser and thicker biofilms maturation, and interspecific protection of 1 species by others, although there are much debate among studies. The fitness of mixed-species biofilms populations is suggested to be of a cooperative, competitive, or neutral nature based on the genetic background of the involved species. Currently, various methods using microarray, confocal microscopy, proteomics, and selective media are being explored for the detection of mixed-species biofilms to resolve the conflict issues. Here, we review recent progress in this emerging field in the context of food safety and propose that novel and alternative techniques like antiquorum sensing, antibiofilms, enzymes, hurdle techniques, and bacteriophages will significantly help to control the formation of mixed-species biofilms for enhanced food safety. The next challenge will be to integrate the fitness and resistance patterns of mixed-species biofilms in the laboratory with those of natural settings.