Assessment of biofilm-forming capacity and multidrug resistance in Staphylococcus aureus isolates from animal-source foods: implications for lactic acid bacteria intervention

Staphylococcus aureus, a Gram-positive bacterium, poses a significant threat to public health and food safety due to its virulence and its ability to develop antimicrobial resistance (AMR). Moreover, S. aureus can form biofilms in food environments, making it difficult to eradicate and pose a major challenge in foodborne illness prevention. The study aimed to investigate the biofilm-forming capabilities and AMR profiles of 107 S. aureus isolates derived from milk, chicken meat, and chicken eggs. Further, the study compared the biofilm formation tendencies between multi-drug resistant (MDR) and non-MDR S. aureus isolates. Additionally, the research explored the antibacterial and anti-biofilm properties of Lactobacillus rhamnosus and Lactobacillus casei, focusing on their aggregation and co-aggregation effects with S. aureus. Around 70.10% of S. aureus isolates were found to be resistant to at least three antibiotic classes. The biofilm assay revealed that 16.82% isolates were strong biofilm formers. The MDR isolates displayed a strong biofilm-forming ability (i.e., 18.67%) and a higher prevalence of biofilm-associated genes [i.e., icaA (53.33%) and icaD (44.0%)] compared to non-MDR isolates. The LAB strain, L. rhamnosus exhibited a 29.06 mm mean antibacterial inhibition zone, an average reduction of 48.19% in biofilm growth, 55.46% auto-aggregation, and 40.61% co-aggregation with S. aureus. Similarly, L. casei demonstrated a 21.80 mm mean antibacterial inhibition zone, an average reduction of 31.56% in biofilm growth, 45.23% auto-aggregation, and 36.81% co-aggregation with S. aureus isolates. This study provides valuable insights into the biofilm formation of MDR S. aureus and underscores the potential of L. rhamnosus and L. casei as bio-control agents. These findings highlight the necessity for additional research into the mechanisms through which LAB strains inhibit pathogenic biofilms and their potential applications in enhancing food safety.