Antibiotic Resistance Trends in Carbapenem-Resistant Gram-Negative Pathogens and Eight-Year Surveillance of XDR Bloodstream Infections in a Western Greece Tertiary Hospital

<b>Background</b>: The increased prevalence of antibiotic resistance among Gram-negative bacteria presents a severe public health challenge, leading to increased mortality rates, prolonged hospital stays, and higher medical costs. In Greece, the issue of multidrug-resistant Gram-negative bacteria is particularly alarming, exacerbated by overuse of antibiotics and inadequate infection control measures. This study aimed to detect the prevalence of extensively drug-resistant (XDR) Gram-negative bacteria in a tertiary hospital in Western Greece over the last eight years from 2016 to 2023. <b>Materials and Methods</b>: In the present study, all Carbapenem-resistant (CR) <i>Acinetobacter baumannii</i>, <i>K. pneumoniae</i> and <i>Pseudomonas aeruginosa</i>. bloodstream isolates from patients hospitalized in the University General Hospital of Patras in Western Greece, from January 2016 to December 2023, were recorded. XDR strains were defined as non-susceptible to at least one agent in all but two or fewer antimicrobial categories (i.e., bacterial isolates remain susceptible to only one or two categories). The prevalence and distribution of these pathogens across different hospital wards and their susceptibility patterns to key antibiotics (aminoglycosides, trimethoprim-sulfamethoxazole, tigecycline, colistin, ampicillin-sulbactam, ceftolozane-tazobactam and ceftazidime-avibactam) were recorded. Results: A total of 1142 blood cultures growing carbapenem-resistant <i>Klebsiella pneumoniae</i> (CRKp), <i>Acinetobacter baumannii</i> (CRAB) and <i>Pseudomonas aeruginosa</i> (CRPsA) were studied. In the present study, we found an increased resistance of both <i>A. baumannii</i> and <i>K. pneumoniae</i> in colistin. <i>Acinetobacter baumannii</i> had colistin resistance rates between 8.4% and 49.3%, showing a stable increase during the study period. <i>K. pneumoniae</i> showed an increased colistin-resistance rate in 2022 and 2023 (46.8% and 31.2%, respectively) Regarding <i>P. aeruginosa,</i> amikacin was almost inactive with a rate 68.4% and 87.5% in 2020 and 2023, respectively. Of all CR isolates, 69.3% were extensively drug-resistant (XDR). <i>Acinetobacter baumannii</i> had the highest percentage of XDR isolates (34.3%), followed by <i>K. pneumoniae</i> (26.8%) and <i>P. aeruginosa</i> (8.1%). Most XDR pathogens were isolated from the ICU (73.4%), followed by the internal medicine units (64%) and surgical units (22%). <b>Conclusions</b>: The rate of antimicrobial resistance and extensive drug resistance is alarmingly high, which calls for strict surveillance, control measures, and antibiotic stewardship to prevent the development of further resistance.