Opportunities for antibiotic optimisation and outcome improvement in patients with negative blood cultures: study protocol for a cluster-randomised crossover trial, the NO-BACT study

BMJ Open. 2019 Dec 18;9(12):e030062. doi: 10.1136/bmjopen-2019-030062.


Introduction: Patients with negative blood cultures (BCx) represent 85%-90% of all patients with BCx taken during hospital admission. This population usually includes a heterogeneous group of patients admitted with infectious diseases or febrile syndromes that require a blood culture. There is very little evidence of the clinical characteristics and antibiotic treatment given to these patients.

Methods and analysis: In a preliminary exploratory prospective cohort study of patients with BCx taken, the clinical/therapeutic characteristics and outcomes/antimicrobial stewardship opportunities of a population of patients with negative BCx will be analysed. In the second phase, using a cluster randomised crossover design, the implementation of an antimicrobial stewardship intervention targeting patients with negative BCx will be evaluated in terms of quality of antimicrobial use (duration and de-escalation), length of hospital stay and mortality.

Ethics and dissemination: This study has been and registered with clinicaltrials.gov. The findings of our study may support the implementation in clinical practice of an antimicrobial stewardship intervention to optimise the use of antibiotics in patients with negative BCx. The results of this study will be published in peer-reviewed journals and disseminated at national and international conferences.

Trial registration number: NCT03535324.

Keywords: antibiotic prescribing; antimicrobial stewardship programs; cluster randomised controlled trial; negative blood culture.

Publication types

  • Clinical Trial Protocol
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / administration & dosage*
  • Anti-Bacterial Agents / adverse effects
  • Antimicrobial Stewardship / methods*
  • Blood Culture
  • Cluster Analysis
  • Cross-Over Studies
  • Humans
  • Infections / drug therapy*
  • Infections / mortality
  • Length of Stay
  • Multicenter Studies as Topic
  • Practice Patterns, Physicians' / statistics & numerical data*
  • Randomized Controlled Trials as Topic


  • Anti-Bacterial Agents

Associated data

  • ClinicalTrials.gov/NCT03535324