Lessons from Four Years (2021–2024) of Klebsiella Pneumoniae Resistance Surveillance Epidemiological Trends in a Romanian Intensive Care Unit

<b>Background:</b><i>Klebsiella pneumoniae</i> represents a major cause of healthcare-associated infections in intensive care units, with resistance profiles ranging from multidrug-resistant to extensively drug-resistant and pandrug-resistant. Critically ill patients, who often require invasive devices and prolonged antibiotic therapy, are especially vulnerable to colonization and infection by these strains. Surveillance data on resistance trends and specimen-specific patterns in Romanian intensive care units (ICUs) remain limited. <b>Methods:</b> We conducted a four-year surveillance study (2021-2024) in a tertiary Romanian ICU, analyzing <i>K. pneumoniae</i> isolates collected from diverse clinical specimens. Resistance phenotypes were classified as MDR, XDR, PDR, or susceptible based on standard definitions. Trends over time were assessed using Cramér's V and correspondence analysis, while stratification by specimen type evaluated associations between anatomical site and resistance profiles. <b>Results:</b> A total of 254 <i>K. pneumoniae</i> isolates were analyzed. MDR strains predominated in 2021 and 2022 but sharply declined by 2024 (from 80% to 8.3%). In parallel, XDR and PDR phenotypes increased substantially, indicating a shift toward more complex resistance profiles. A significant temporal association was found (Cramér's V = 0.43), with 2024 marked by a sharp decline in MDR isolates and a predominance of XDR and PDR phenotypes, reflecting an advanced resistance profile. Specimen-type analysis showed tracheal aspirates as the main reservoir for resistant strains, followed by urine and blood cultures, with a weaker but meaningful association (Cramér's V = 0.24). <b>Conclusions:</b> These findings reveal a change in resistance patterns in ICU-acquired <i>K. pneumoniae</i> infections, with MDR strains being displaced by XDR and PDR phenotypes. These findings highlight the urgent need for time- and specimen-informed resistance monitoring and adaptive antimicrobial stewardship. Without targeted interventions, gains made in controlling MDR strains risk being rapidly eclipsed by the spread of highly resistant organisms.