Evaluating the costs of Escherichia coli bloodstream infections: a population-based cohort study in a large metropolitan Canadian region

Objectives: We evaluated the costs of susceptible and resistant Escherichia coli bloodstream infections (BSIs) in adults. Secondary outcomes were the impact of BSI on length of stay (LOS), readmissions and death. Methods: We examined a population-based retrospective cohort of blood cultures from 2011 to 2018 in Calgary, Canada, linked to microcosting and gross costing data. Propensity score matching was completed, and costs were compared between no BSI and E. coli BSI over 90 days using linear regression. Results: A total of 4581 BSIs in 89 673 adults experienced E. coli bacteraemia during the study period. The mean cost of an E. coli BSI at 90 days was $39 072 (SD: $95 747) in adults. Ceftriaxone-resistant (CRO-R) E. coli, resistant to fluoroquinolones (FQ) and trimethoprim/sulfamethoxazole, compared with susceptible E. coli BSI resulted in the greatest mean cost at $53 899 and the highest odds of readmission, increased LOS, and death. Conclusions: E. coli BSI is associated with substantial costs. Total cost differences were highest in those with CRO-R E. coli with resistance to FQ and trimethoprim/sulfamethoxazole. Over the study period, bacteraemia sec-ondary to these strains alone, added over $9 million to costs for healthcare in the Calgary Zone.