We performed a multicentre retrospective cohort study including 606,649 acute inpatient episodes at 10 European hospitals in 2010 and 2011 to estimate the impact of antimicrobial resistance on hospital mortality, excess length of stay (LOS) and cost. Bloodstream infections (BSI) caused by third-generation cephalosporin-resistant Enterobacteriaceae (3GCRE), meticillin-susceptible (MSSA) and -resistant Staphylococcus aureus (MRSA) increased the daily risk of hospital death (adjusted hazard ratio (HR) = 1.80; 95% confidence interval (CI): 1.34–2.42, HR = 1.81; 95% CI: 1.49–2.20 and HR = 2.42; 95% CI: 1.66–3.51, respectively) and prolonged LOS (9.3 days; 95% CI: 9.2–9.4, 11.5 days; 95% CI: 11.5–11.6 and 13.3 days; 95% CI: 13.2–13.4, respectively). BSI with third-generation cephalosporin-susceptible Enterobacteriaceae (3GCSE) significantly increased LOS (5.9 days; 95% CI: 5.8–5.9) but not hazard of death (1.16; 95% CI: 0.98–1.36). 3GCRE significantly increased the hazard of death (1.63; 95% CI: 1.13–2.35), excess LOS (4.9 days; 95% CI: 1.1–8.7) and cost compared with susceptible strains, whereas meticillin resistance did not. The annual cost of 3GCRE BSI was higher than of MRSA BSI. While BSI with S. aureus had greater impact on mortality, excess LOS and cost than Enterobacteriaceae per infection, the impact of antimicrobial resistance was greater for Enterobacteriaceae.

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Within the last decade, methicillin-resistant Staphylococcus aureus belonging to clonal complex 398 (CC398) has become a worldwide threat associated with livestock. More recently, methicillin-susceptible S. aureus (MSSA) belonging to CC398 have been increasingly reported as a cause of invasive infections in patients without livestock contact. We investigated risk factors associated with CC398 bloodstream infections (BSIs) compared with non-CC398 BSIs with a case-control study in a French university Hospital. From January 2010 to December 2014, nonduplicate Staphylococcus aureus (SA) isolates responsible for BSIs in adult patient were typed to identify those belonging to CC398. Each adult patient with a CC398 SA BSI (cases) was matched with 2 non-CC398 SA BSI controls randomly selected on the basis of the time at risk, the unit of hospitalization and susceptibility to methicillin. We retrospectively extracted the clinical information from electronic medical records and used conditional logistic regression for univariate and multivariate analyses. We identified 67 CC398 isolates among the 770 SA responsible for BSI in adult patients. All CC398 isolates were susceptible to methicillin. The proportion of CC398 among MSSA increased steadily from 4.6% in 2010 to 15.1% in 2013 and then stabilized at 13.8% in 2014. Factors significantly associated with CC398 MSSA BSIs were healthcare-associated infection (odds ratio (OR) 3.02, 95% confidence interval (CI) 1.19-7.63), history of neurologic disease (OR 2.51, 95% CI 1.13-5.65) and 30-day mortality (OR 2.44, 95% CI 1.23-4.85).