The involvement of the biliary tract in bacteremia caused by Staphylococcus aureus may be more likely to develop in certain patients and aggressive treatment should be considered, according to a study results presented at IDWeek, held from October 2 to October 6 in Washington, DC.

A variety of infections are caused by S aureus but origins of this bacteria from the biliary tract is rare and there are scant case reports and no clinical studies available to provide any data on the involvement of the biliary tract. Therefore, this matched case-control study was conducted to assess the clinical characteristics and outcomes of S aureus bacteremia from a biliary source.

In total, 1818 patients with S aureus bacteremia were included in the study; of these patients, 2% were cases of biliary S aureus bacteremia. From 2008 to 2018, all adult patients with S aureus bacteremia were observed for 12 weeks. Biliary S aureus bacteremia was defined as the case of S aureus isolated from blood culture with appropriate clinical indications of biliary infection (ie, fever, abdominal pain, or jaundice, abdominal tenderness or liver enzyme elevation with obstructive pattern). Based on age, gender, hospital ward, and case year, biliary S aureus bacteremia cases were matched in a 1:3 ratio to control patients with catheter-related S aureus bacteremia.

Results suggested that biliary S aureus bacteremia was rare and developed mainly in patients with pancreaticobilary cancer and in patients who recently received broad-spectrum.  Among the 42 patients with biliary S aureus bacteremia, 76.2% patients had a solid tumor involving pancreaticobiliary tract or liver, 71.4% patients had a biliary drainage stent, 57.1% patients had a recent broad-spectrum antibiotics exposure, and 33.3% patients had a biliary procedure-related infection. Compared with 126 patients who had catheter-related S aureus bacteremia, patients with biliary S aureus bacteremia were more likely to have a solid tumor, a lower APACHE II score, and community-onset S aureus bacteremia, and were less likely to have a metastatic infection (P =.03). Results suggested that a high Charlson comorbidity index, biliary S aureus bacteremia, and a solid tumor were associated with 12-week mortality and a multivariate analysis confirmed that a high Charlson comorbidity index (adjusted odds ratio [aOR], 1.32) and biliary S aureus bacteremia (aOR, 5.5) were independent risk factors for 12-week mortality. These high mortality rates may be a due to underlying cancers.

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Overall, the study authors concluded that, “When biliary tract infection caused by S. aureus is clinically suspected, early aggressive treatment for [S aureus bacteremia] should be considered.”

Reference

Yang E, Bae S, Seo H, et al. Clinical characteristics and outcomes of Staphylococcus aureus bacteremia from a biliary source. Poster presented at: IDWeek 2019; October 2-6, 2019; Washington, DC.