Evaluation of the frequency and change of antimicrobial resistance over years of methicillin-resistant Staphylococcus aureus clinical isolates at Suleyman Demirel University Hospital

We aimed to evaluate the distribution and antibiotic resistance rates of 517 MRSA isolated in our hospital between 2014 and 2022. Methicillin resistance and antibiotic susceptibility were determined using conventional methods and Phoenix™ automated system. Antibiotic susceptibilities were evaluated according to the EUCAST recommendations. The rate of MRSA among S. aureus isolates was determined as 16.12%. Over nine years There was a decrease in 2016 and an increase in 2022 in MRSA rates. MRSA was most frequently isolated from blood samples and in anesthesia intensive care unit. Vancomycin MIC values were higher between 2015 and 2018 and lower in 2020. Linezolid MIC values were lower in 2017 and higher in 2019. There was a decrease in resistance rates for clindamycin, gentamicin, tetracycline, and rifampicin, while an increase was observed in resistance rates for trimethoprim-sulfamethoxazole and fusidic acid. MIC values were higher for teicoplanin and rifampin in 2014, 2015, and 2016, for tetracycline in 2017, 2020, and 2021, for fusidic acid in 2021, and for quinupristin-dalfopristin in 2014. MIC values were lower for trimethoprim-sulfamethoxazole and gentamicin in 2022. Resistance rates were significantly higher in tissue, sputum, and tracheal aspirate compared to synovial fluid for erythromycin, in tissue and urine compared to sputum for clindamycin, in tissue compared to synovial fluid, wound, and sputum for gentamicin, in tissue and tracheal aspirate compared to abscess for rifampicin, and in catheter compared to tracheal aspirate for fusidic acid. The MIC values of antibiotics should be closely monitored for successful empirical treatment of MRSA infections. The resistance pattern of our hospital, have been revealed with our data. Our study is the first study that compare resistance rates and MIC values of antibiotics in MRSA isolates over the years and sample types together in our country. Further studies are needed to investigate the significance of the differences we observed in MRSA resistance rates according to sample type. Keywords: Antimicrobial resistance, MRSA, Minimum inhibitory concentration, sample type, surveillance