Marlieke de Kraker and colleagues reflect on the need for better global estimates for the burden of antimicrobial resistance.

The authors calculate excess mortality, excess hospital stay, and related hospital expenditure associated with antibiotic-resistant bacterial bloodstream infections (Staphylococcus aureus and Escherichia coli) in Europe.

We investigated bacteraemia trends for five major bacterial pathogens, Staphylococcus aureus, Escherichia coli, Streptococcus pneumoniae, Enterococcus faecalis and Enterococcus faecium, and determined how expanding antimicrobial resistance influenced the total burden of bacteraemias in Europe. Aetiological fractions of species and antibiotic phenotypes were extracted from the European Antimicrobial Resistance Surveillance System (EARSS) database for laboratories, which consistently reported between 2002 and 2008. Trend analyses used generalized linear models. Robustness of results was assessed by iterative analysis for different geographic regions. From 2002 to 2008, the overall number of reports increased annually by 6.4% (95% confidence interval (CI) 6.2-6.5%), from 46 095 to 67 876. In the subset of laboratories providing denominator information, the overall incidence increased from 0.58/1000 patient-days to 0.90/1000 patient-days (7.2% per year; 95% CI 6.9-7.5%). The frequency of reported bacteraemia isolates of S. aureus and Streptococcus pneumoniae increased moderately, while increase in E. coli and Enterococcus faecium was more pronounced. Bacteraemias caused by methicillin-resistant S. aureus increased until 2005 (7.6% per year; 95% CI 6.1-9.1%), and then decreased (-4.8% per year; 95% CI -6.1 to -3.5%), whereas the number attributable to methicillin-sensitive S. aureus increased continuously (3.4% per year; 95% CI 3.0-3.7). Increasing rates of E. coli were mainly caused by antibiotic-resistant phenotypes. Our data suggest that the burden of bacterial bloodstream infection has been increasing for all species during EARSS surveillance. Trends were mainly driven by resistant strains and clearly dissociated between resistant and susceptible isolates. It appears that infections with resistant clones add to rather than replace infections caused by susceptible bacteria. As a consequence, expansion of antibiotic resistance creates an additional strain on healthcare systems.

Antimicrobial resistance poses a growing threat to public health and the provision of health care. Its surveillance should provide up-to-date and relevant information to monitor the appropriateness of therapy guidelines, antibiotic formulary, antibiotic stewardship programmes, public health interventions, infection control policies, and antimicrobial development. In Europe, although the European Antimicrobial Resistance Surveillance Network provides annual reports on monitored resistant bacteria, national surveillance efforts are still fragmented and heterogeneous, and have substantial structural problems and issues with laboratory data. Most incidence and prevalence data cannot be linked with relevant epidemiological, clinical, or outcome data. Genetic typing, to establish whether trends of antimicrobial resistance are caused by spread of resistant strains or by transfer of resistance determinants among different strains and species, is not routinely done. Furthermore, laboratory-based surveillance using only clinical samples is not likely to be useful as an early warning system for emerging pathogens and resistance mechanisms. Insufficient coordination of surveillance systems of human antimicrobial resistance with animal surveillance systems is even more concerning. Because results from food surveillance are considered commercially sensitive, they are rarely released publicly by regulators. Inaccurate or incomplete surveillance data delay a translational approach to the threat of antimicrobial resistance and inhibit the identification of relevant target microorganisms and populations for research and the revitalisation of dormant drug-discovery programmes. High-quality, comprehensive, and real-time surveillance data are essential to reduce the burden of antimicrobial resistance. Improvement of national antimicrobial resistance surveillance systems and better alignment between human and veterinary surveillance systems in Europe must become a scientific and political priority, coordinated with international stakeholders within a global approach to reduce the burden of antimicrobial resistance.