Background/Objectives: Carbapenem-resistant Klebsiella pneumoniae (CRKp) remains a critical driver of antimicrobial resistance (AMR) in hospital settings worldwide. Methods: This study examined trends in CRKp bloodstream infections over a seven-year period (2019–2025) in a tertiary care hospital in Greece, with particular attention given to resistance patterns and patient outcomes, including the impact of the COVID-19 pandemic. Results: A total of 671 non-duplicate CRKp isolates were analyzed and classified into three groups: KPC producers (67.4%), dual carbapenemase producers (dual CP) (17.4%), and single metallo-β-lactamase (MBL) producers (15.2%). Overall incidence showed a slight but non-significant increase over time. KPC-producing strains rose significantly until 2022 (p < 0.001), followed by a marked decline (p < 0.001). In contrast, dual CPs—mainly KPC combined with VIM or NDM—and single-MBL producers, particularly NDM, increased steadily, indicating a notable epidemiological shift. Resistance to aminoglycosides and tigecycline increased around 2021, followed by partial declines, whereas colistin resistance demonstrated a continuous upward trend throughout the study period. Despite phenotypic differences, overall mortality remained high, with no statistically significant differences between groups (p = 0.37), likely reflecting either the severity of patients’ clinical condition or inadequate empirical antibiotic therapy. Conclusions: This study highlights a dynamic evolution in CRKp epidemiology with decreasing KPC dominance and increasing prevalence of MBL- and dual CP strains. This transition, which became evident during and after the COVID-19 pandemic, underscores ongoing epidemiological adaptation and the urgent need for improved antimicrobial stewardship, rapid diagnostics, and broader access to effective therapies.

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKp) remains a critical driver of antimicrobial resistance (AMR) in hospital settings worldwide. Methods: This study examined trends in CRKp bloodstream infections over a seven-year period (2019–2025) in a tertiary care hospital in Greece, with particular attention to resistance patterns and patient outcomes, including the impact of the COVID-19 pandemic. Results: A total of 671 non-duplicate CRKp isolates were analyzed and classified into three groups: KPC producers (67.4%), dual carbapenemase producers (17.4%), and single metallo-β-lactamase (MBL) producers (15.2%). Overall incidence showed a slight but non-significant increase over time. KPC-producing strains rose significantly until 2022 (p<0.001), followed by a marked decline (p<0.001). In contrast, dual carbapenemase producers—mainly KPC combined with VIM or NDM—and single-MBL producers, particularly NDM, increased steadily, indicating a notable epidemiological shift. Resistance to aminoglycosides and tigecycline increased around 2021, followed by partial declines, whereas colistin resistance demonstrated a continuous upward trend throughout the study period. Despite phenotypic differences, overall mortality remained high, with no statistically significant differences between groups (p = 0.37), likely reflecting either the severity of patients’ clinical condition or inadequate empirical antibiotic therapy. Conclusions: This study highlights a dynamic evolution in CRKp epidemiology with decreasing KPC dominance and increasing prevalence of MBL- and dual carbapenemase- producing strains. This transition, which became evident during and after the COVID-19 pandemic, underscores ongoing epidemiological adaptation and the urgent need for improved antimicrobial stewardship, rapid diagnostics, and broader access to effective therapies.

Background/Objectives: The aim of the present study is to report an outbreak of bloodstream infections caused by Serratia marcescens in patients undergoing postoperational procedures in the Cardiothoracic Department and to describe the epidemiological investigations and control measures undertaken. A cluster of bacteremia due to Serratia marcescens was identified in blood cultures from postoperative patients in the Cardiothoracic Surgery Department in November 2023. Methods: Active surveillance by the hospital’s prevention and control team was initiated. Interviews with nurses and sanitary personnel and reviews of the most common procedures, such as hand washing, bladder catheterization, and intravenous catheter care, were performed. Culturing samples from hospital personnel, postoperative patients, and the environment, including pressure transducers, tap water, soap, therapeutic solutions, antiseptics, respirators, and various intravenous preparations, were drawn up. Overall, 225 samples were collected, including 149 blood cultures, and these were all sent to the Hospital’s Microbiology Laboratory. Results: Twenty-three out of forty-seven postoperative patients had positive blood cultures for Serratia marcescens. All the postoperative patients involved in the outbreak received cefepime according to antimicrobial susceptibility testing. Three pre-prepared flushing syringes were found to be positive for Serratia marcescens as well. The Cardiothoracic Department was kept under surveillance with hand hygiene measures, infusion preparation, medical device use, and cleaning procedures reviewed by the infection’s prevention and control team. Conclusions: Undoubtedly, nosocomial outbreaks represent an important health issue regarding morbidity, mortality, and costs. Timely interventions by the hospital’s infection prevention and control team may be life-saving under these circumstances.