Trends in Antimicrobial Resistance at a Greek Tertiary Hospital over a 7-Year Period, Including the COVID-19 Pandemic

Abstract

Background/Objectives: Antimicrobial resistance (AMR) remains a major global threat, with the COVID-19 pandemic influencing its dynamics, although its overall impact remains uncertain. This study analyzed seven-year AMR trends, including the pandemic period, in a tertiary care hospital in Greece that served as a COVID-19 referral center. Methods: Multiresistant bacteria isolated from all biological specimens of hospitalized patients between January 2018 and December 2024 were recorded and classified as multidrug- (MDR), extensively drug- (XDR), or pandrug-resistant (PDR). Overall AMR was defined as the sum of these categories. Annual incidences of overall AMR, its categories, and predominant Gram-negative (A. baumannii, K. pneumoniae, P. aeruginosa) and Gram-positive [methicillin-resistant S. aureus (MRSA), vancomycin-resistant Enterococcus (VRE)] pathogens were analyzed for the entire hospital and by sector (medical, intensive care unit [ICU], surgical). Bloodstream infection (BSI) AMR was also evaluated. Trend analysis was performed using Joinpoint regression. Results: Overall AMR exhibited a transient peak around 2021 across the hospital, except in the surgical sector. A significant rise in average annual percentage change (AAPC) occurred only in the medical sector (p < 0.001). PDR incidence increased hospital-wide (p < 0.001). K. pneumoniae, P. aeruginosa, MRSA, and VRE rose significantly in the medical sector, whereas ICU incidences remained largely stable despite the 2021 peak. A. baumannii showed no significant change. BSI-related AMR increased in the medical sector (p < 0.001) but not in the ICU (p = 0.2). Conclusions: Although overall AMR did not rise uniformly, PDR organisms increased hospital-wide. These findings support updating empiric therapy guidelines, reinforcing infection prevention measures, and translating surveillance data into targeted stewardship actions to enhance patient care.