Changes in hospitals’ daily practice due to COVID-19 pandemic may have an impact on antimicrobial resistance (AMR). We aimed to assess this possible impact as captured by the Greek Electronic System for the Surveillance of Antimicrobial Resistance (WHONET-Greece). Routine susceptibility data of 17,837 Gram-negative and Gram-positive bacterial isolates from blood and respiratory specimens of hospitalized patients in nine COVID-19 tertiary hospitals were used in order to identify potential differences in AMR trends in the last three years, divided into two periods, January 2018–March 2020 and April 2020–March 2021. Interrupted time-series analysis was used to evaluate differences in the trends of non-susceptibility before and after the changes due to COVID-19. We found significant differences in the slope of non-susceptibility trends of Acinetobacter baumannii blood and respiratory isolates to amikacin, tigecycline and colistin; of Klebsiella pneumoniae blood and respiratory isolates to meropenem and tigecycline; and of Pseudomonas aeruginosa respiratory isolates to imipenem, meropenem and levofloxacin. Additionally, we found significant differences in the slope of non-susceptibility trends of Staphylococcus aureus isolates to oxacillin and of Enterococcus faecium isolates to glycopeptides. Assessing in this early stage, through surveillance of routine laboratory data, the way a new global threat like COVID-19 could affect an already ongoing pandemic like AMR provides useful information for prompt action.

The objective of this study was to analyze the characteristics that contribute to the successful dissemination of VIM-producing Pseudomonas aeruginosa (P. aeruginosa), belonging to ST111 and ST235, in a Greek hospital. A total of 120 non-repetitive P. aeruginosa, which had meropenem minimal inhibitory concentrations (MICs) greater than 2 mg/L, were studied. VIM-encoding genes were amplified and sequenced within their integrons. Isolates were typed by multilocus sequence typing (MLST). Six VIM-producers, representative of different integron structures and sequence types (STs), were completely sequenced using Illumina platform. Sixty-one P. aeruginosa were confirmed to produce VIM-type carbapenemases. ST111 dominated (n = 34) among VIM-producers, while 15 VIM-producers belonged to ST235. The bla_VIM-like genes were located in three integron types, including In59, In595 and In1760, which were integrated into P. aeruginosa chromosomes. Whole genome sequencing (WGS) data demonstrated that ST111 and ST235 MBL producers carried several resistance and virulence genes. Additionally, the presence of type I-C and type I-E clustered regularly interspaced short palindromic repeats (CRISPR)/Cas locus was observed in ST235 and ST395 isolates, respectively. In conclusion, our findings confirmed the clonal spread of ST111 P. aeruginosa, carrying the VIM-2-encoding integron In59, in the University Hospital of Larissa (UHL). In addition, they highlighted the important role of high-risk clones, ST111 and ST235, in the successful dissemination and establishment into hospital settings of clinically important pathogens carrying resistance determinants.

Introduction: The combination of ceftazidime−avibactam (CAZ-AVI) with aztreonam (ATM) may be an option for the treatment of infections due to metallo-β-lactamases (MBLs) producing bacteria, as recommended by current guidelines. MBLs protect the pathogen from any available β-lactam/β-lactamase inhibitor (BL/BLI). Moreover, in vitro and clinical data suggest that double carbapenem therapy (DCT) may be an option for such infections. Materials and Methods: This retrospective study was conducted in two mixed intensive care units (ICUs) at the University Hospital of Larissa, Thessaly, Greece, and the General Hospital of Larissa, Thessaly, Greece, during a three-year period (2022−2024). Mechanically ventilated patients with bloodstream infection (BSI) caused by K. pneumoniae resistant to all BL/BLI combinations were studied. Patients were divided into three groups: in the first, patients were treated with CAZ-AVI + ATM; in the second, with DCT; and in the third, with antibiotics other than BL/BLIs that presented in vitro susceptibility. The primary outcome of the study was the change in Sequential Organ Failure Assessment (SOFA) score between the onset of infection and the fourth day of antibiotic treatment. Secondary outcomes were SOFA score evolution during the treatment period, total duration of mechanical ventilation (MV), ICU length of stay (LOS), and ICU mortality. Results: A total of 95 patients were recruited. Among them, 23 patients received CAZ-AVI + AZT, 22 received DCT, and 50 patients received another antibiotic regimen which was in vitro active against the pathogen. The baseline characteristics were similar. The mean (SE) overall age was 63.2 (1.3) years. Mean (SE) Acute Physiology and Chronic Health Evaluation II (APACHE II) and SOFA scores were 16.3 (0.6) and 7.6 (0.3), respectively. The Charlson Index was similar between groups. The control group presented a statistically lower SOFA score on day 4 compared to the other two groups [mean (SE) 8.9 (1) vs. 7.4 (0.9) vs. 6.4 (0.5) for CAZ-AVI + ATM, DCT and control group, respectively (p = 0.045)]. The duration of mechanical ventilation, ICU LOS, and mortality were similar between the groups (p > 0.05). Comparison between survivors and non-survivors revealed that survivors had a lower SOFA score on the day of BSI, higher PaO₂/FiO₂ ratio, higher platelet counts, and lower lactate levels (p < 0.05). Septic shock was more frequent among non-survivors (60.3%) in comparison to survivors (27%) (p = 0.0015). Independent factors for mortality were PaO₂/FiO₂ ratio and lactate levels (p < 0.05). None of the antibiotic regimens received by the patients was independently associated with survival. Conclusions: Treatment with CAZ-AVI + ATM or DCT may offer similar clinical outcomes for patients suffering from BSI caused by K. pneumoniae strains resistant to all available BL/BLIs. However, larger studies are required to confirm the findings.

Background/Objectives: Antimicrobial resistance (AMR) has increased significantly over the years, contributing to a real challenge in the intensive care unit (ICU). The emergence of metallo-beta-lactamases (MBLs) has contributed to the protection of pathogens against all current beta-lactam/beta-lactamase inhibitors (BL/BLIs), including the newer ceftazidime–avibactam (CAZ-AVI), meropenem–vaborbactam, and imipenem–relebactam. Treatment of such infections is challenging. In vitro and clinical data suggest that combinations of CAZ-AVI with aztreonam (ATM) and the use of two different carbapenems (double carbapenem therapy, DCT) may be an option for MBL-producing pathogens. The aim of our study was to evaluate the effectiveness of the combination CAZ-AVI + ATM and the effectiveness of DCT against MBL-producing K. pneumoniae infections in the critically ill, mechanically ventilated patients. Methods: This is a retrospective study conducted in the two ICUs of hospitals in central Greece. Mechanically ventilated patients admitted to the ICU were included in the study if they developed an infection by MBL-producing K. pneumoniae. Patients were divided into three groups: the first one consisted of patients who were treated with CAZ-AVI plus ATM (CAZ-AVI + ATM group), and the second group consisted of patients who received DCT (DCT group). The third group included patients who received appropriate antibiotic therapy other than CAZ-AVI + ATM and DCT (control group). The primary outcome of the study was the evolution of the sequential organ failure assessment (SOFA) score, and secondary outcomes were duration of mechanical ventilation (MV), ICU length of stay (LOS), and, finally, ICU mortality. Results: 108 patients were included in the study. 35 (32%) in the CAZ-AVI + ATM group, 31 (29%) in the DCT group, and the remaining 42 (39%) patients in the control group. The SOFA score was not statistically different on day 1, day 4, and day 7 of the infection among the three groups (p > 0.05). Duration of MV and ICU LOS were also similar. Finally, mortality did not differ between the groups [20 patients (57.1%) vs. 18 (58.1%) vs. 25 (59.5%) for CAZ-AVI + ATM, DCT and control group, respectively, p = 0.98]. Comparison between survivors and non-survivors revealed that independent risk factors for mortality were SOFA score at day 1 of infection and medical cause of admission (p < 0.05). Conclusions: Treatment with CAZ-AVI + ATM or DCT presented similar efficacy with appropriate antibiotic therapy for infections caused by MBL-producing K. pneumoniae strains. Larger studies are required to confirm the findings.

This study aimed to investigate the marked increase in bla_NDM-1-positive Acinetobacter baumannii isolates (20% of all CRAB isolates) observed in a tertiary-care hospital in Central Greece during 2025. Thirty bla_NDM-1-producing carbapenem-resistant A. baumannii (CRAB) isolates were selected and subjected to whole-genome sequencing for molecular typing and characterization of antimicrobial resistance determinants and virulence-associated genes. The majority of the isolates (22/30) belonged to ST2^Pasteur (18 strains), ST85^Pasteur (2 strains) and ST2493^Pasteur (2 strains), all previously identified in 2023. The remaining eight strains belonged to newly detected STs, such as ST1^Pasteur (six strains) and ST2806^Pasteur (two strains). All strains carried the bla_NDM-1 gene on the Tn7382. The high prevalence of bla_NDM-1-positive CRAB represents not only a local threat but also a national concern, as patients from our hospital are frequently transferred to other healthcare facilities or long-term care centers across the country, creating a substantial risk for further dissemination of these strains. Routine molecular screening for bla_NDM-1-positive CRAB may represent a valuable strategy for limiting further dissemination.