ScopeThis ESCMID guideline provides evidence-based recommendations to support a selection of appropriate antibiotic use practices for patients seen in the emergency department (ED) and guidance for their implementation.The topics addressed in this guideline are: 1) Do biomarkers or rapid pathogen tests improve antibiotic prescribing and/or clinical outcomes? 2) Does taking blood cultures in common infectious syndromes improve antibiotic prescribing and/or clinical outcomes? 3) Does watchful waiting without antibacterial therapy or with delayed antibiotic prescribing reduce antibiotic prescribing without worsening clinical outcomes in patients with specific infectious syndromes? 4) Do structured culture follow-up programs in patients discharged from the ED with cultures pending improve antibiotic prescribing?MethodsAn expert panel was convened by ESCMID and the guideline chair. The panel selected in consensus the four most relevant AMS topics according to pre-defined relevance criteria. For each main question for the four topics, a systematic review was performed, including randomized controlled trials and observational studies. Both clinical outcomes as well as stewardship process outcomes related to antibiotic use were deemed relevant. The literature searches were conducted between May 2021 and March 2022. In April 2022, the panel members were formally asked to suggest additional studies that were not identified in the initial searches. Data were summarized in a meta-analysis if possible or otherwise summarized narratively. The certainty of the evidence was classified according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria. The guideline panel reviewed the evidence per topic critically appraising the evidence and formulated recommendations through a consensus-based process. The strength of the recommendations was classified as strong or weak. To substantiate the implementation process, implementation trials or observational studies describing facilitators/barriers for implementation were identified from the same searches and were summarized narratively.RecommendationsThe recommendations on the use of biomarkers and rapid pathogen diagnostic tests focus on the initiation of antibiotics in patients admitted through the ED. Their effect on the discontinuation or de-escalation of antibiotics during hospital stay was not reported, neither was their effect on hospital infection prevention and control practices. The recommendations on watchful waiting (i.e., withholding antibiotics with some form of follow-up) focus on specific infectious syndromes for which the primary care literature was also included. The recommendations on blood cultures focus on the indication in three common infectious syndromes in the ED explicitly excluding patients with sepsis or septic shock.Most recommendations are based on very-low- and low-certainty of evidence, leading to weak recommendations or, when no evidence was available, to best practice statements. Implementation of these recommendations needs to be adapted to the specific settings and circumstances of the ED. The scarcity of high-quality studies in the area of antimicrobial stewardship in the ED highlights the need for future research in this field.