Genotypic Detection of agr Classes Using Uniplex-PCR and Quantitative Assessment of Biofilm titer in MRSA Isolates from Clinical Samples

Background: Methicillin-resistant Staphylococcus aureus (MRSA) has a significant clinical concern due to its resistance to multiple antibiotics and enhanced virulence, often associated with the accessory gene regulator (agr) system and biofilm formation. Objectives: This study aimed to determine the distribution of accessory gene regulator (agr) classes I–IV among methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates and to quantitatively assess their biofilm formation using a microtiter plate assay. Methodology: A total of 150 clinical samples were collected from patients suffering from tonsillitis, skin infections, and urinary tract infections, all were obtained from Samarra General Hospital- Iraq over a six-month period from June to November 2024, and screened for MRSA using microbiological and molecular methods and for detection of agr classes Biofilm formation was detected using micro-titter plate assay. Results: Fifty isolates were confirmed as MRSA. Genotyping revealed agr class I as the most prevalent (59%), followed by agr classes III, II, and IV. All isolates demonstrated ability of biofilm-forming, with agr class I strains exhibiting the strongest biofilm production. Moreover, agr class I isolates showed the highest rates of multidrug resistance and were exclusively linked to tonsillitis cases. Conclusion: These findings suggest that agr class I plays a prominent role in MRSA pathogenicity through its association with biofilm formation and antibiotic resistance. Detection of agr classes may assist in the development of targeted treatment strategies.