The Impact of the COVID-19 Pandemic on Antimicrobial Resistance Trends in a Tertiary Care Teaching Hospital: A Ten-Year Surveillance Study

<b>Background/Objectives:</b> The COVID-19 pandemic accelerated the inappropriate use of antibiotics, amplifying the global threat of antimicrobial resistance (AMR), particularly in resource-limited healthcare settings. This study investigated AMR patterns in a tertiary care hospital, focusing on the impact of the COVID-19 pandemic on invasive bacterial pathogens. <b>Methods:</b> This retrospective observational study was conducted at the University Clinical Centre of the Republic of Srpska, analyzing AMR data from invasive bacterial isolates collected between 2015 and 2024, and assessing correlations between antibiotic utilization and resistance patterns during the study periods. <b>Results:</b> Among 4718 invasive bacterial isolates, <i>Acinetobacter</i> spp. (26.7%) and <i>K. pneumoniae</i> (20.8%) were the most prevalent. A significant increase in invasive isolates was observed during the COVID-19 period, particularly for <i>K. pneumoniae</i> (<i>p</i> = 0.003), <i>P. aeruginosa</i> (<i>p</i> = 0.017), <i>Acinetobacter</i> spp. (<i>p</i> = 0.013), and <i>E. faecium</i> (<i>p</i> = 0.028). The highest multidrug-resistant (MDR) rates were observed in <i>Acinetobacter</i> spp. (97% during COVID-19) and <i>K. pneumoniae</i> (>80% post-COVID-19). Resistance increased significantly in <i>K. pneumoniae</i> to cephalosporins, fluoroquinolones, and carbapenems, and in <i>P. aeruginosa</i> and <i>Acinetobacter</i> spp. to carbapenems, while <i>P. aeruginosa</i> resistance to aminoglycosides declined. Strong correlations were found between carbapenems use and <i>Acinetobacter</i> spp. resistance (r = 0.861, <i>p</i> = 0.001), and vancomycin use and <i>E. faecalis</i> resistance (r = 0.798, <i>p</i> = 0.006). Moderate correlations were also observed between carbapenems use and resistance of <i>K. pneumoniae</i> and <i>P. aeruginosa</i>. <b>Conclusions:</b> These findings highlight the profound impact of the COVID-19 pandemic on AMR dynamics, particularly among Gram-negative pathogens, and underscore the urgent need for strengthened antimicrobial stewardship and targeted surveillance to curb the spread of MDR pathogens, especially in resource-limited hospitals.