Biofilms formed by human skin microbiota on stainless steel surfaces: implications for pathogen control in food environments

• Skin-derived microbiota readily forms biofilms on stainless steel surfaces. • Pathogen inhibition was strongest against Staphylococcus aureus biofilms. • Competitive biofilms were enriched in Firmicutes, especially Bacillus spp. • Bacillus cereus emerged as a key driver of antagonism but poses food safety risk. • Metagenomic profiling may improve hygiene monitoring on food-contact surfaces. Human handling is a major route of microbial transfer in food processing, yet the ability of human skin microbiota to establish biofilms on food-contact surfaces and to modulate pathogen behaviour remains poorly understood. This study investigated whether naturally shed dermal microbial communities can colonize stainless steel and how their taxonomic composition influences the attachment and persistence of major foodborne pathogens. Skin microbiota from 60 donors were allowed to form biofilms on stainless steel coupons, followed by challenge assays with Escherichia coli, Salmonella enterica serovar Typhimurium, and Staphylococcus aureus . Almost all samples (98.3%) formed dense biofilms exceeding 6 log CFU cm⁻², with 60.3% reaching levels commonly associated with mature biofilms (≥7 log CFU cm⁻²). Final biofilm biomass was not correlated with initial inoculum size, indicating that surface colonization was driven primarily by community composition rather than microbial load. Pathogen interactions were species-specific: E. coli generally overgrew dermal biofilms, whereas inhibition was observed in 11.7% of cases for S. Typhimurium and in 63.2% for S. aureus , including complete suppression in a subset of samples. 16S rRNA gene sequencing revealed that competitive biofilms were enriched in Firmicutes, particularly Bacillales, with Bacillus spp. expanding from minor constituents in dermal swabs to dominant taxa in biofilms. The frequent detection of Bacillus cereus in inhibitory communities underscores a dual role as both antagonist and potential foodborne hazard. Overall, these findings demonstrate that dermal-derived biofilms act as structured microbial microecosystems whose composition, rather than total biomass, determines their ecological impact on pathogen persistence, highlighting the need to consider resident surface microbiota in hygiene management and microbial risk assessment.