BIOFILM FORMATION BY STAPHYLOCOCCUS AUREUS ISOLATES FROM ANIMAL SOURCES IN SINGLE- AND MIXED-CULTURES

Staphylococcus aureus is a major opportunistic pathogen capable of forming resilient biofilms on biotic and abiotic surfaces, contributing to persistent infections and antibiotic resistance. Polymicrobial biofilms, in which S. aureus coexists with bacteria or fungi, further complicate treatment and affect disease outcomes. This study evaluated the biofilm-forming capacity of S. aureus isolates from animal and food sources in single- and dual-species cultures with Candida albicans, Pseudomonas aeruginosa, and reference strain of S. aureus. Thirty-one strains (including 28 S. aureus) were grown in biofilm-promoting media. Biofilm biomass was quantified by crystal violet staining in 96-well plates and by the qualitative tube assay. Results showed that 18% of S. aureus isolates formed a visible biofilm on glass tubes, whereas 50% produced biomass above the cutoff (OD660 > 0.028) on polystyrene plates, mainly as weak or moderate biofilm formers (mean OD660 values between 0.029 and 0.094). In mixed cultures, most dual-species biofilms exhibited reduced total biomass compared to monocultures. Keywords: Staphylococcus aureus; Candida albicans; Pseudomonas aeruginosa; biofilm; polymicrobial interactions.