Clinical characteristics and outcomes of Staphylococcus aureus bacteremia from a biliary source.

Staphylococcus aureus is a virulent gram-positive organism, which rarely involves the biliary tract. This study aimed to analyze the clinical characteristics and outcomes of S. aureus bacteremia (SAB) originating from the biliary tract by comparing them with those of catheter-related SAB and biliary Klebsiella pneumoniae bacteremia. A matched case-control study within a prospective observational cohort of patients with SAB was conducted. Biliary SAB was defined as the isolation of S. aureus from blood cultures with symptoms and signs of biliary infection. Biliary SAB patients were matched (1:3) with the control groups: patients with catheter-related SAB and biliary Klebsiella pneumoniae bacteremia. Out of 1818 patients with SAB enrolled in the cohort, 42 (2%) had biliary SAB. Majority of these patients had solid tumors involving the pancreaticobiliary tract or liver, biliary drainage stent, and/or recent broad-spectrum antibiotic exposure. Patients with biliary SAB were more likely to have community-onset SAB, solid tumors, and lower APACHE II score than those with catheter-related SAB. They were less likely to have community-acquired infection and solid tumors and more likely to have lower Charlson comorbidity index and higher APACHE II score as compared with biliary K. pneumoniae bacteremia. The 12-week mortality in the biliary SAB group was higher than those in other control groups (60% vs. 20% and 14%). After adjusting for confounding factors, biliary SAB was independently associated with higher mortality. Biliary SAB is relatively rare. When it is clinically suspected, early aggressive treatment should be considered due to high mortality.