Phenotypic and Genotypic Study of Biofilm Formation of Multi-Drug Resistant Staphylococcus aureus Isolated from Different Clinical Infections/Iraq

Background: Staphylococcus aureus is a main pathogen linked to nosocomial and community acquired infection and reason essential public health problem. Objective: The goal of this study was to assess the phenotypic and genotypic capacity for biofilm formation among MDR Staphylococcus aureus isolates from different clinical infections. Methodology: From November, 2024 to June, 2025, A total number of (230) specimens were collected randomly from patients with different clinical infections of different hospitals / Iraq. The microbiological assays were used to identify S.aureus isolate that exposed to antimicrobial resistance test towards 18 antibiotic types by using disc diffusion test and Biofilm formation detection of S. aureus isolates by using Micro Titer Plate with Congo Red Agar Method and PCR technique. Results: Out of 230 specimens, only (80) of S. aureus isolates were subjected to antimicrobial susceptibility test towards 18 antibiotic types, The results showed the highest rate of S. aureus resistance was Penicillin G (97.5%) and the low rate was Vancomycin (0%). Out of 80 specimens, 45(56.25%) isolates were MDR S. aureus and only 41(91.2%) isolates showed biofilm formation by CRA Method while 45 (100%) isolates were positive by Microtiter plate assay and using PCR technique to identify biofilm formation genes in 45 MDR S. aureus, IcaA gene were (88.8%) and the IcaD gene (88.8 %), whereas clfA gene (82.2%). Conclusion: This study concluded that MDR S. aureus isolates from patients with different clinical infections are capable of biofilm formation.