Dynamics of Antimicrobial Resistance and Antimicrobial Consumption in a Secondary-Care Hospital in Serbia, 2019–2022: A Retrospective Observational Study

Antimicrobial resistance (AMR) is accelerating and driven by antimicrobial use. Hospital consumption and resistance data remain scarce in Serbia. This retrospective study assessed the prevalence of infectious agents among hospitalized patients (2019–2022), distribution and AMR rates of Escherichia coli and Klebsiella pneumoniae, antimicrobial consumption, and associations between AMR and antibiotic use (Spearman’s correlation). All bacterial isolates were included for species-frequency analyses. For AMR and specimen distribution, repeat isolates of E. coli and K. pneumoniae per patient were excluded. Among 10,780 isolates, E. coli remained most frequent (24.7% in 2019; 24.3% in 2022), whereas K. pneumoniae increased from 7.7% to 16.9% (p < 0.001). E. coli resistance to cephalosporins, fluoroquinolones, and piperacillin/tazobactam increased significantly from 2019 to 2022 (p < 0.05). K. pneumoniae resistance increased to most agents (p < 0.001), with meropenem resistance rising from 11.7% to 52.0%. Multidrug resistance rose from 27.3% to 35.4% for E. coli (2020–2022; p = 0.006) and from 62.4% to 82.9% for K. pneumoniae (2019–2022; p < 0.001). Total hospital antibiotic consumption nearly doubled from 57 to 111.8 Defined Daily Doses per 100 bed days (2019–2021) and decreased to 52.0 (2022). Temporal concurrence of increased antimicrobial use during COVID-19 and escalating resistance underscores the need for strengthened surveillance and stewardship.