Prevalence and Antimicrobial Resistance Trends of Staphylococcus aureus in a University Hospital: A 6.5-Year Retrospective Analysis

Introduction: Staphylococcus aureus is a major pathogen causing infections in both community and hospital settings.Surveillance of this organism is essential for effective planning of preventive strategies.This study aimed to evaluate changes in the isolation frequency and antimicrobial resistance patterns of Staphylococcus aureus strains in a university hospital over recent years. Materials and Methods:In this retrospective cross-sectional study, data on Staphylococcus aureus strains isolated at xxx University Faculty of Medicine Hospital between January 2019 and June 2025 were collected.Demographic information of patients and antimicrobial resistance prociles of the isolates were analyzed.Changes in strain prevalence and resistance rates over the years were assessed using linear regression analysis.Results: A total of 3,514 Staphylococcus aureus strains were examined, including 861 (24.5%) community-acquired and 2653 (75.5%) hospital-acquired.The median prevalence of Staphylococcus aureus among all cultures was 9.96%, showing a nonsignicicant variation from 9.2% to 11.57% over the study period.Comparison of pre-and post-pandemic periods revealed a signicicant increase in hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) (p < 0.05), whereas changes in community-acquired MRSA were not signicicant.Among hospital isolates, methicillin resistance approximately doubled, whereas no signicicant change was observed in community-acquired strains.Methicillin-resistant strains exhibited two-to seven-fold higher resistance to several antimicrobials, including quinolones, aminoglycosides, macrolides, and co-trimoxazole, compared to methicillin-susceptible strains.During the study period, resistance to amikacin, gentamicin, and erythromycin signicicantly decreased, while resistance to tetracycline and clindamycin increased.Conclusion: Although the overall prevalence of Staphylococcus aureus remained stable, methicillin resistance increased steadily, particularly in hospital-acquired strains.Targeted strategies to control these highly resistant strains should be a priority.