Molecular study of Chlorhexidine resistance in Methicillin Resistant <i>Staphylococcus aureus</i>

Methicillin Resistant Staphylococcus aureus (MRSA) is a main cause of severe human infections. The aim this study was to detect chlorhexidine resistance MRSA by phenotypic and genotypic methods. Fifty strains were isolated from different hospitals Mansoura University over period one year December 2021 till November 2022. antimicrobial susceptibility test conducted the disk diffusion method, except for vancomycin which detected minimum inhibitory concentration (MIC) determination using microdilution broth method. MIC towards (CHG) determined Qac genes (qacA/B1, qacA/B2, smr, norA) Polymerase Chain Reaction (PCR). Transmission electron microscope used cell-wall thickness susceptible resistant strains. results exhibited that greatest isolates Penicillin (100%) Ceftazidime Vancomycin (72%). Decreased CHG at ≥4 mg/L in 24 (48%). highest smr (100%), norA (50%), qacA/B2 (45.8%), with low prevalence qacA/B1 (4.16%). It found strain high had more thickened cell wall than strain.