Although prompt administration of an appropriate antimicrobial therapy (AAT) is crucial
for reducing mortality in the general population with community-onset bacteremia, the prognostic
effects of delayed AAT in older individuals with febrile and afebrile bacteremia remain unclear. A
stepwise and backward logistic regression analysis was used to identify independent predictors of
30-day mortality. In a 7-year multicenter cohort study involving 3424 older patients (≥65 years) with
community-onset bacteremia, febrile bacteremia accounted for 27.1% (912 patients). A crucial association
of afebrile bacteremia and 30-day mortality (adjusted hazard ratio [AHR], 1.69; p < 0.001)
was revealed using Cox regression and Kaplan–Meier curves after adjusting for the independent
predictors of mortality. Moreover, each hour of delayed AAT was associated with an average increase
of 0.3% (adjusted odds ratio [AOR], 1.003; p < 0.001) and 0.2% (AOR, 1.002; p < 0.001) in the
30-day crude mortality rates among patients with afebrile and febrile bacteremia, respectively, after
adjusting for the independent predictors of mortality. Similarly, further analysis based on Cox regression
and Kaplan–Meier curves revealed that inappropriate empirical therapy (i.e., delayed AAT
administration > 24 h) had a significant prognostic impact, with AHRs of 1.83 (p < 0.001) and 1.76 (p
< 0.001) in afebrile and febrile patients, respectively, after adjusting for the independent predictors
of mortality. In conclusion, among older individuals with community-onset bacteremia, the dissimilarity
of the prognostic impacts of delayed AAT between afebrile and febrile presentation was evident.
