Molecular profiling of methicillin and vancomycin resistant <i>Staphylococcus aureus</i> isolates from Baghdad hospitals

Introduction: Oxacillin and vancomycin are commonly used to treat Staphylococcus aureus infections. Molecular typing of S. aureus is essential for understanding resistance patterns. Objectives: This study aims to determine the phenotypic and genotypic features of S. aureus (methicillin-resistant S. aureus [MRSA] and vancomycin-resistant S. aureus [VRSA]) isolates obtained from various sources, including wounds, skin, urine, vaginal swabs, ear swabs, and body fluids, from samples of different outpatients and hospitalized patients in several key hospitals and medical laboratories in Baghdad governorate, Iraq. Patients and Methods: In this cross-sectional study, biochemical diagnostic tests were conducted on the isolates, coagulase-positive isolates were collected. These isolates were confirmed through ordinary microbiological and molecular testing. Antibiotic screening test was determined. A phenotypic and genotypic biofilm forming ability and other characteristics were investigated. Molecular typing of the isolates was conducted using polymerase chain reaction (PCR). Results: Out of 130 coagulase-positive cocci, 72 were identified as MRSA and 19 as VRSA. Biofilm assay results showed that 22 (18.92%) isolates had strong biofilm formation, 24 (18.46%) had moderate formation, 26 (20.00%) had weak formation, and 58 (44.62%) had no biofilm formation. The MRSA biofilm-associated gene mecA was detected in 37 (80.4%) of the isolates, while in VRSA, mecA was detected in 13 (68.42%). Additionally, the cna gene was present in five cases (26.32%) of the VRSA isolates. Genes were characterized based on P-value into true-false and presence-absence counts. Antimicrobial screening showed that most isolates were sensitive to gentamicin, with higher resistance observed for oxacillin and rifampin. The staphylococcal cassette chromosome mec (SCCmec) patterns for MRSA and VRSA were determined using PCR results. Conclusion: This study indicates that S. aureus, including MRSA and VRSA, should be considered significant opportunistic pathogens across all age groups and clinical units. Gentamicin and tigecycline are recommended for treating certain S. aureus infections