Comparison of biofilm production and virulence genes distribution among human and canine isolates of Staphylococcus aureus

Background: Staphylococcus aureus is an important human and animal pathogen that can cause a wide range of infections due to numerous virulence factors. Aims: The aim of this study was to compare biofilm formation ability with different virulence factors such as bacterial motility, genes encoding biofilm associated proteins, and Panton-Valentine leukocidin (PVL) among human and canine isolates of S. aureus. Methods: A total of 60 human (30 methicillin sensitive S. aureus (MSSA) and 30 methicillin resistant S. aureus (MRSA)) and 17 canine (all MSSA) isolates of S. aureus were tested for the capability of biofilm production, motility assay, and presence of genes encoding virulence factors: ica (encoding intercellular adhesion), bap (encoding biofilm-associated protein), fnbA (encoding fibronectin-binding protein A), cna (encoding collagen-binding protein), and pvl (encoding PVL). Results: Animal isolates of S. aureus performed better biofilm production than the human strains (P=0.042), as well as human MSSA compared to the MRSA isolates (P=0.013). Our results showed that cna, fnbA, and ica genes (67.5%, 66.2%, and 42.9%, respectively) were more prevalent than bap and pvl genes (0%, and 7.8%, respectively). The ica gene was significantly more prevalent in human isolates compared to animal isolates (n=31/60 vs. n=2/17, P=0.008), whereas the cna gene was more frequent in animal isolates than in human ones (n=15/17 vs. n=37/60, P=0.0201). Significant correlations were found between the biofilm formation of animal isolates, and the presence of fnbA (P=0.029) and ica genes (P=0.001). Conclusion: This study showed a correlation between biofilm production and the presence of certain biofilm-related genes in animal isolates, as well as stronger biofilm production among MSSA human and animal isolates.