Characterization and Antimicrobial Resistance Profiles of Biofilm Forming Strains of Staphylococcus aureus Isolated from Skin Lesions

<i>Staphylococcus aureus</i> is an important human pathogen known for its versatility and ability to cause a wide range of infections. The aim of this study was to isolate and identify <i>S. aureus</i> from skin lesions from human patients, to determine antimicrobial resistance and biofilm formation potential at phenotypic and genotypic levels, as well as to verify the activity of efflux pump production. Out of 51 samples collected from skin lesions of various etiologies, 13 isolates were identified as <i>S. aureus</i>. All isolates showed the ability to form biofilms, which correlated with the presence of the <i>icaABCD</i>, <i>agrA</i>, <i>srtA</i>, <i>clfAB</i>, and <i>fnbAB</i> genes, while the <i>bap</i> gene was absent. The highest rates of resistance were observed for ampicillin (69.2%) and gentamicin (46.2%), as well as for erythromycin and clindamycin (38.5%). The <i>mecA</i> gene was present in two isolates, but phenotypic resistance to methicillin was confirmed in only one of them, suggesting possible heterogeneous expression or regulated activity of resistance mechanisms. The <i>mecC</i> gene was not present in any isolate. Efflux pump production was observed in only three isolates, showing weak to intermediate levels. These findings indicate the high biofilm potential and variable antimicrobial resistance of <i>S. aureus</i> clinical isolates, which pose a challenge for the treatment of emerging skin infections.