Data on the adequacy or inadequacy of antimicrobial therapy for serious infections caused by Staphylococcus aureus in Europe are currently insufficient. The objective of this study, conducted in hospitals in 9 Western European countries, was to assess the adequacy of antibiotic therapy for the bacteremia caused by S. aureus, the identification of factors that determine the choice of inadequate therapy and the effect of inadequate treatment on patient outcomes.

In this retrospective cohort study, we analyzed data from adult patients who received staphylococcal bacteremia caused by methicillin-sensitive or methicillin-resistant Staphylococcus aureus (MSSA or MRSA) in 60 randomly selected hospitals from November 1, 2007 to 31 December 2007. Adequate therapy has been defined as the intravenous administration of at least one antimicrobial drug, to which the sensitivity of the strain S. aureus in vitro, in 2 days after the onset of staphylococcal bacteremia.

The study analyzed 334 episodes of bacteremia caused by S. aureus (257 cases of MSSA infection and 77 episodes of bacteremia caused by MRSA). Almost a third of patients (94 patients, 28%) received inadequate empirical antibiotic therapy (21% in the MSSA infectious group and 52% in the MRSA infectious group). Length of hospital stay before staphylococcal bacteremia and infection caused by methicillin-resistant strains of Staphylococcus aureus were the most common factors associated with the appointment of inadequate treatment (correlated odds ratio 1.01 [ 95% confidence interval 1.00-1.03] and 3.7, [95% confidence interval 2.2-6.4], respectively). Patient age (OS 1.06, 95% confidence interval 1.03-1.10), Charlson comorbidity index (OS 2.1, 95% confidence interval 1.2-3.6), severe sepsis or septic shock (OS 2.7, interval 95% confidence 1.5-4.8) and stay in the intensive care unit at the start of the bacteremia (OS 2.9, 95% confidence interval 1.5-5.6), but not inadequate treatment (OSh 0.7, 95% confidence interval 0.4-1.3-1.10), resulted in an increase in 30-day mortality.

Thus, the study showed that the insufficiency of empirical antibiotic therapy is very common in Western Europe and is clearly associated with an infection caused by strains of MRSA Staphylococcus aureus.