Adequacy of Antimicrobial Treatment and Outcome of Staphylococcus aureus Bacteremia in 9 Western European Countries

Background. Little is known about the incidence of inadequate treatment of severe Staphylococcus aureus infection in Europe. We aimed to evaluate the adequacy of antibiotic therapy for S. aureus bacteremia (SAB), to identify determinants of inadequate treatment, and to determine the effect of inadequate treatment on patient outcome in a representative selection of hospitals in 9 Western European countries. Methods. In this retrospective cohort study, all adult patients with SAB (due to methicillin-susceptible S. aureus [MSSA] or methicillin-resistant S. aureus [MRSA]) who were admitted to 60 randomly selected hospitals from 1 November 2007 through 31 December 2007 were included. Adequate antimicrobial therapy was defined as intravenous administration of at least 1 antibiotic to which the isolate showed in vitro susceptibility that was initiated within 2 days after onset of SAB. Results. A total of 334 SAB episodes (257 due to MSSA and 77 due to MRSA) were included. Ninety-four patients (28%) received inadequate empirical therapy (21% in the MSSA group and 52% in the MRSA group). Both length of stay before SAB onset and methicillin-resistant infection were associated with inadequate therapy, with adjusted odds ratios (ORs) of 1.01 (95% confidence interval [CI], 1.00-1.03) and 3.7 (95% CI, 2.2-6.4), respectively. Age (OR, 1.06; 95% CI, 1.03-1.10), Charlson comorbidity score (OR, 2.1; 95% CI, 1.2-3.6), severe sepsis or septic shock (OR, 2.7; 95% CI, 1.5-4.8), and intensive care unit stay at onset of SAB (OR, 2.9; 95% CI, 1.5-5.6) but not inadequate treatment (OR, 0.7; 95% CI, 0.4-1.3) were associated with increased 30-day mortality. Conclusion. Inadequate empirical antimicrobial therapy for SAB is common in Western Europe and is strongly associated with infection caused by MRSA. In this study, inadequate treatment was not associated with increased 30-day mortality rates.