Longitudinal trends in community-onset bacteraemia caused by ceftriaxone non-susceptible Escherichia coli, Proteus mirabilis, Klebsiella oxytoca , and Klebsiella pneumoniae (2016–2024)

Abstract Background The increasing prevalence of ESBL-producing Enterobacterales complicates treatment and worsens outcomes. However, contemporary data describing the prevalence and temporal trends in established risk factors for community-onset ceftriaxone non-susceptible (CRO-NS) bacteraemia remain limited. Methods This retrospective cohort study included adults with community-onset bacteraemia due to Escherichia coli, , Klebsiella pneumoniae, Klebsiella oxytoca, or Proteus mirabilis, evaluated at Phoebe Putney Health System (Albany, GA) between January 2016 and November 2024. Community-onset was defined by the first positive blood culture collected in the ER or ≤48 h of presentation. CRO susceptibility was determined by institutional antimicrobial susceptibility testing. Polymicrobial bacteraemia, incomplete records, or interfacility transfer were excluded. Results Among 1392 patients with community-onset bacteraemia, 127 (9.1%) were due to CRO-NS isolates, with E. coli accounting for 83%. The prevalence of CRO-NS isolates doubled over the study period, increasing from 7% in 2016 to 16% in 2024 (P = 0.008), reflecting an approximate annual increase of 1%. Most patients were older adults (median age 67), female (57%), and Black or African American (53%), with multiple comorbidities (median Charlson Comorbidity Index 5). A urinary source was most common (67%). Recent antibiotic use (≤30 days: 37%; ≤90 days: 61%) and prior hospitalization (≤90 days: 39%; ≤1 year: 61%) were frequent. Most established risk factors remained stable over time. Conclusion Community-onset CRO-NS bacteraemia more than doubled over nine years, driven primarily by E. coli. These findings demonstrate the expanding burden of antimicrobial resistance in the community and emphasize the importance of local surveillance and risk-based empiric prescribing strategies.