Staphylococcus aureus bacteremia among elderly vs younger adult patients -Comparison of clinical features and mortality

Background: Previous studies give conflicting results regarding the effect of age on outcomes in Staphylococcus aureus bacteremia (SAB). These studies have been limited by retrospective design or small sample size. Methods: We conducted a prospective cohort study of 385 patients with SAB a ged 18 to 90 years. The setting was a large academic medical center. Wt obs erved patients from diagnosis of SAB to discharge or death. Discharged pati ents were contacted 12 weeks after their first positive culture findings. D ata were collected on demographics, comorbid conditions, focus of infection , length of stay, and outcome. Primary outcomes were total mortality and de ath due to SAB. Results: Comparisons were made between 145 patients, aged 66 to 90 years, a nd 240 patients, aged 18 to 60 years. Forty-three (29.7%) of the elderly pa tients and 36 (15%) of the younger patients died. Death directly attributab le to SAB occurred in 21 (14.5%) older and 15 (6.3%) younger patients. Afte r adjusting for confounding variables, older patients continued to have hig her total mortality (odds ratio, 2.21; 95% confidence interval, 1.32-3.70), and higher mortality from SAB (odds ratio, 2.30; 95% confidence interval, 1.13-4.69). Infection with methicillin-resistant S aureus was associated wi th higher total mortality in the elderly (odds ratio, 2.59; 95% confidence interval, 1.23-5.43). Conclusions: Staphylococcus aureus bacteremia among the elderly is associat ed with high mortality. Both total mortality and mortality directly attribu table to SAB are more than twice as likely in older patients. Infection wit h methicillin-resistant S aureus carries a worse prognosis than infection w ith methicillin-sensitive S aureus in the elderly.