Broader Time Window Feasible to Determine Appropriate Antibiotics for Bloodstream Infection

The risk for 30-day mortality was found to be significantly associated with time to appropriate antibiotic therapy administration following blood culture collection in patients with bloodstream infections (BSIs), according to study findings published in Clinical Infectious Diseases.

Researchers conducted a retrospective cohort study using data captured from the electronic health records of 10,628 adult patients admitted to Karolinska University Hospital in Stockholm, Sweden for treatment of BSIs between January 2012 and December 2019. They used multivariable logistic regression to analyze the risk for 30-day mortality in relation to timing of appropriate antibiotic therapy administration.

A total of 10,628 episodes of BSI were included in the final analysis, representing 9,192 patients. Of these patients, the median age was 69 years, 56.8% were women, and 85.3% had community-onset BSI. Of the BSI episodes, the most commonly identified causative pathogens were Escherichia coli, Staphylococcus aureus, and viridans streptococci. Following blood culture collection, the majority of results were available to physicians within 24 to 72 hours.

The researchers performed a multivariable logistic regression analysis, with adjustments for Charlson comorbidity index score, immunosuppressed status, age, polymicrobial BSI, source of infection, calendar year of onset, hospital-onset BSI, and severity of illness.

After 30 days, the crude mortality rate was 11.8% for BSI episodes overall, 13.7% for episodes (n=3266) in which appropriate therapy was administered within 1 hour of blood culture collection, and 25.3% for episodes (n=608) in which septic shock was present.

Multivariable logistic regression showed inappropriate antibiotic therapy at 12 hours following blood culture collection was associated with a significantly increased 30-day mortality risk (adjusted odds ratio, 1.17; 95% CI, 1.01-1.37). The risk for 30-day mortality gradually increased with time as the researchers observed similar trends when inappropriate therapy occurred at 24, 48, and 72 hours following blood culture collection; however, mortality did not increase despite a lack of appropriate therapy at 1, 3, and 6 hours following culture collection.

Study limitations include the retrospective design, potential residual confounding, the use of only in vitro susceptibility testing to determine appropriate antibiotic therapy, and the possibility that differences in antibiotic dosing, treatment durations, and administration routes affected patient outcomes.

“These results indicate a benchmark for providing rapid microbiological diagnostics of blood cultures,” the researchers concluded.