The dual-species biofilm formed by Staphylococcus aureus and Pseudomonas fluorescens exhibited enhanced resistance to disinfectants

Multi-species biofilms present a greater threat to the dairy industry than single-species biofilms due to their complex characteristics. This study examined the formation of biofilms by dairy contaminants Staphylococcus aureus and Pseudomonas fluorescens (single/co-culture) on stainless steel, and their resistance to chlorine dioxide and quaternary ammonium compounds. The findings indicated that the dual-species biofilm exhibited significantly higher biomass, cell activity, and extracellular polymeric substances production than single-species biofilms, along with a denser biofilm structure in dual-species biofilm and increased resistance to both disinfectants. Remarkably, relative quantification analysis using RT-qPCR revealed an interaction: the presence of P. fluorescens markedly upregulated the icaA and icaD genes in S. aureus. This genetic modulation was directly correlated with increased production of polysaccharide intercellular adhesion and EPS, which are crucial for biofilm maturation and structural integrity. This study offers a theoretical foundation for the hazard control of multi-species biofilms in the dairy industry.