Sepsis is a medical emergency and life-threatening condition due to a dysregulated host response to infection, with unacceptably high morbidity and mortality. Similar to acute myocardial infarction or cerebral vascular accident, sepsis is a severe and continuous time-dependent condition. Thus, in the case of sepsis, early and adequate administration of antimicrobials must be a priority, ideally within the first hour of diagnosis, simultaneously with organ support. As a consequence of the emergence of multidrug-resistant pathogens, the choice of antimicrobials should be performed according to the local pathogen patterns of resistance. Individual antimicrobial optimization is essential to achieve adequate concentrations of antimicrobials, to reduce adverse effects, and to ensure successful outcomes, as well as preventing the emergence of multidrug-resistant pathogens. The loading dose is the administration of an initial higher dose of antimicrobials, regardless of the presence of organ dysfunction. Further doses should be implemented according to pharmacokinetics/pharmacodynamics of antimicrobials and should be adjusted according to the presence of renal or liver dysfunction. Extended or continuous infusion of beta-lactams and therapeutic drug monitoring can help to achieve therapeutic levels of antimicrobials. Duration and adequacy of treatment must be reviewed at regular intervals to allow effective de-escalation and administration of short courses of antimicrobials for most patients. Antimicrobial stewardship frameworks, leadership, focus on the optimal duration of treatments, de-escalation, and novel diagnostic stewardship approaches will help us to improve patients the process of care and overall quality of care.

Background/Objectives: Routine biomarkers and clinical scores do not directly assess functional immune responsiveness in suspected sepsis. We evaluated whether the TNF-α Release Assay (TARA), a whole-blood LPS-induced functional assay, is associated with an early cytokine-low immune phenotype in Emergency Department (ED) patients. Methods: In this prospective single-center cohort, adults with suspected sepsis and NEWS2 ≥ 3 were sampled at presentation, at 4 h and, when available, at 24 h. Immune phenotypes were defined independently of TARA by unsupervised k-means clustering of 12 circulating cytokines at 4 h, and a continuous Low-Response Cytokine Score (LRCS) was derived, with higher values indicating lower global cytokine concentrations. Results: Among 152 patients, three phenotypes were identified: C1 cytokine-low (n = 56), C2 inflammatory/intermediate (n = 63), and C3 IFN-γ/MCP-3/IL-17A-high (n = 33). Indicative TARA low-response status was independently associated with a higher LRCS after adjustment for clinical covariates and procalcitonin (PCT), both at presentation (β = 0.33; 95% CI, 0.14–0.53; p = 0.001) and at 4 h (β = 0.38; 95% CI, 0.19–0.57; p < 0.001). Indicative TARA low-response results at 4 h were most frequent in C1 and least frequent in C3 (75% vs. 45%). Exploratory clinical comparisons showed lower recorded early escalation in C1, whereas Sepsis-3 final diagnosis and in-hospital mortality were similar across phenotypes. Conclusions: A TARA low-response status was independently associated with an early circulating cytokine-low phenotype defined without reference to TARA or outcomes, providing information complementary to routine biomarkers and clinical severity scores. These exploratory findings support TARA as a complementary functional immune readout but require external validation and clinical-impact evaluation.