Attributable length of stay, mortality risk and costs of bacterial healthcare-associated infections in Australia: a retrospective case-cohort study

Unbiased estimates of the health and economic impact of healthcare-associated infections (HAIs) are scarce and focus largely on patients with bloodstream infection (BSI). We sought to estimate the hospital length of stay (LOS), mortality and costs of HAIs and the differential effect on patients with an antimicrobial resistance (AMR) infection.

A multi-site, retrospective case-cohort of all acute-care hospital admissions with a positive culture of one of the five organisms of interest (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus or Enterococcus faecium) from January 1, 2012 through December 30, 2016. Data linkage was used to generate a dataset of statewide hospital admissions and pathology data. Patients with bloodstream, urinary or respiratory tract infections were included in the analysis and matched to a sample of uninfected patients. We use multistate survival models to generate LOS and logistic regression to derive mortality estimates.

20,390 cases were matched to 75,635 uninfected control patients. The overall incidence of infections due to the five studied organisms was 116.9 cases per 100,000 patient days with E. coli urinary tract infections (UTI)s contributing the largest proportion (51 cases per 100 000 patient days). The impact of a UTI on hospital stay was moderate across the five studied pathogens. Resistance significantly increased hospital stay for patients with third-generation cephalosporin-resistant K. pneumoniae bloodstream infection (BSI) (extra 4.6 days) and methicillin-resistant S. aureus (MRSA) BSI (extra 2.9 days). Consequently, healthcare costs of these infections were higher, compared to corresponding drug-sensitive strains.

The health burden remains highest for BSIs, however the UTIs and respiratory tract infections (RTI) contributed most to the healthcare system expenditure.