Trends in antimicrobial resistance and antibiotic use before and during the COVID-19 pandemic in a university research and practice hospital in Türkiye

Introduction Antibacterial resistance and the increasing number of infections caused by multidrug-resistant bacteria threaten human health worldwide. The coronavirus disease 2019 (COVID-19) pandemic may have influenced antibacterial resistance patterns through changes in infection control practices and antibiotic prescribing. Aim This single-centre, retrospective study aimed to describe changes in bacterial distribution, antibacterial resistance and antibiotic consumption in a university research and practice hospital before and during the COVID-19 pandemic. Methods We analysed routine microbiology and pharmacy records from hospitalized patients between 01.04.2018 and 31.03.2022. The two years before 01.04.2020 were defined as the pre-pandemic period and the two years after 01.04.2020 as the pandemic period. Bacteria isolated from blood, urine and lower respiratory tract cultures, together with their antimicrobial susceptibility profiles, were compared between periods according to EUCAST criteria. Antibiotic consumption was calculated as defined daily doses (DDD) per 1000 inpatient-days for commonly used agents. No patient-level clinical data or ward/ICU stratification were available. Results A total of 7275 isolates from 47,729 culture samples were obtained in the pre-pandemic period and 5794 isolates from 47,210 samples during the pandemic. Coagulase-negative staphylococci remained the most frequently isolated species from blood cultures, Escherichia coli from urine cultures and Acinetobacter baumannii from lower respiratory tract cultures in both periods. Extended-spectrum β-lactamase (ESBL) rates and carbapenem resistance in E. coli and Klebsiella pneumoniae increased significantly during the pandemic, whereas teicoplanin and linezolid resistance in coagulase-negative staphylococci decreased. Carbapenem resistance in A. baumannii also decreased. Overall antibiotic consumption increased for most agents, particularly cephalosporins, carbapenems, aminoglycosides and fluoroquinolones, while vancomycin use decreased. Conclusion In this single-centre, retrospective analysis, the overall distribution of major bacterial species remained largely stable before and during the COVID-19 pandemic, whereas important changes were observed in antimicrobial resistance profiles and antibiotic consumption. The increase in ESBL and carbapenem resistance in Enterobacterales, together with higher use of broad-spectrum antibiotics, underlines the need for strengthened antimicrobial stewardship and continuous local surveillance.