Trend of β-lactam Resistance in Escherichia coli and Klebsiella pneumoniae Bacteremia and Clinical Characteristics of Cefotaxime-susceptible Extended-spectrum β-lactamase-producing Isolates

Abstract

Background: This study aimed to evaluate the trend of β-lactam resistance in Escherichia coli and Klebsiella pneumoniae bacteremia, the prevalence of cefotaxime-susceptible extendedspectrum β-lactamase-producing (ESBL) E. coli and K. pneumoniae, and the clinical characteristics of these infections. Methods: A retrospective study was conducted in a tertiary hospital in Korea between 2011 and 2020. All patients with E. coli or K. pneumoniae bacteremia were identified, along with the results for the antibiotic susceptibility and ESBL production test for each isolate. Results: Of 15 706 E. coli and K. pneumoniae bacteremia episodes, only 10 (0.06%) were caused by cefotaxime-susceptible ESBL-producing isolates, and their prevalence remained low during the study period. The proportion of ESBL-producing isolates gradually increased from 23.1% to 29.5%, whereas the proportion of carbapenem-resistant isolates rapidly increased from 0.9% to 12.1%. Furthermore, the proportion of carbapenem-resistant K. pneumoniae increased significantly and surpassed that of carbapenem-susceptible ESBL-producing K. pneumoniae in 2020. In a matched case-control study, the baseline characteristics of patients with cefotaxime-susceptible ESBL E. coli and K. pneumoniae bacteremia were similar to those with cefotaxime-resistant infections. There was no significant difference in 30-day mortality between patients with cefotaxime-susceptible and cefotaxime-resistant ESBL E. coli and K. pneumoniae bacteremia. Conclusion: The prevalence of cefotaxime-susceptible ESBL E. coli and K. pneumoniae bacteremia and its mortality were very low, supporting the current guidelines for elective ESBL testing. The rapidly increasing carbapenem resistance is a concern.