Background: To prioritize healthcare investments, ranking of infections caused by antibiotic-resistant bacteria should be based on accurate incidence data.

Objectives: We performed a systematic review to estimate frequency measures of antimicrobial resistance for six key bacteria causing bloodstream infections (BSI) in European countries.

Data sources: We searched PubMed, Web of Science, Embase databases, and the ECRAID-Base Epidemiological-Network platform.

Study eligibility criteria: We included studies and surveillance systems assessing resistance-percentage, prevalence, or incidence-density of BSI because of carbapenem-resistant Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, and Escherichia coli, third-generation cephalosporins-resistant E. coli and K. pneumoniae, vancomycin-resistant Enterococcus faecium, and methicillin-resistant Staphylococcus aureus.

Methods: Reviewers independently assessed published data and evaluated study quality with the modified Joanna Briggs Institute critical appraisal tool. Pooled estimates were determined using random effects meta-analysis. Consistency of data was assessed using random effects meta-regression (Wald test, p > 0.05).

Results: We identified 271 studies and 52 surveillance systems from 32 European countries. Forty-five studies (16%) reported on BSI, including 180 frequency measures most commonly as resistance-percentage (88, 48.9%). Among 309 frequency measures extracted from 24 (46%) surveillance systems, 278 (89%) were resistance-percentages. Frequency measures of methicillin-resistant S. aureus and vancomycin-resistant E. faecium BSI were more frequently reported from Southern Europe and Western Europe (80%), whereas carbapenem-resistant P. aeruginosa BSI from Northern Europe and Western Europe (88%). Highest resistance-percentages were detected for carbapenem-resistant A. baumannii (66% in Central Eastern Europe) and carbapenem-resistant K. pneumoniae (62.8% in Southern Europe). Pooled estimates showed lower resistance-percentages in community versus healthcare-associated infections and in children versus adults. Estimates from studies and surveillance systems were mostly consistent among European regions. The included data was of medium quality.

Discussion: Pathogen-specific frequency measures of antimicrobial resistance in BSI are insufficient to inform antibiotic stewardship and research and development strategies. Improving data collection and standardization of frequency measures is urgently needed.