Cost of bacteraemia caused by methicillin-resistant vs. methicillin-susceptible Staphylococcus aureus in Spain: a retrospective cohort study

The aim of this study was to determine the impact on healthcare resource utilization and associated costs of bacteraemia due to methicillin-resistant Staphylococcus aureus (MRSA) vs. methicillin-susceptible S. aureus (MSSA) strains in Spain. An observational, retrospective, cohort multicentre study was conducted during 2005. The target population comprised Spanish patients with S. aureus bacteraemia (five and ten cases per hospital for resistant and susceptible strains, respectively). The resources used were obtained from the hospital patient records. The unit costs were obtained from the participating hospitals and from Spanish databases; the costs of a bacteraemic episode were estimated from resource utilization results and expressed in euros (€). Univariate sensitivity analyses were performed. The clinical records of 366 valid patients with S. aureus bacteraemia (121 MRSA and 245 MSSA) from 27 Spanish hospitals were reviewed. Resource use per bacteraemic episode was higher for MRSA cases than for MSSA cases, with longer antibiotic treatment (3.1 additional days) and greater length of hospital stay (LOS) (2.2 additional days), more diagnostic tests, and higher rates of admission to the intensive-care unit (ICU) (7.6%). As a consequence, a higher cost per episode was incurred, with an additional €1205 in episodes of MRSA infections (1.12-fold increase). The main drivers of the cost difference were the higher rates of ICU admission and hospital re-admission and increased LOS. The analysis confirmed that there were additional costs due to resistant strains, ranging from €293 to €5188. Overall, MRSA was associated with higher costs in bacteraemic patients, and this was attributable mainly to the greater rate of ICU admissions and increased LOS.