Infections caused by multidrug resistant microbes have a direct attributable mortality of more than 1.27 million people every year. For patients with serious systemic infections, every hour without effective antimicrobial therapy contributes to ≥6.4% increased risk of death. Existing pathology pipelines to match targeted antibiotic therapy with an individual infection can take days to return actionable results: new innovations are desperately needed. Peritoneal dialysis (PD) is an advantageous form of renal replacement therapy. The technique requires the insertion of a surgical catheter into the abdominal wall: for these patients, the risk of peritonitis (a life-threatening infection of the abdominal cavity) is a real barrier to commencing and remaining on therapy.
We conducted an observational cohort study of PD peritonitis patients to demonstrate the power of acoustic-enhanced flow cytometry to reduce the timeline for confirmation of infection and prediction of antimicrobial susceptibility from days to hours. Across a representative subsample of clinical peritonitis effluent samples (n=104) we developed a workflow to enumerate microbial cells and classify samples as “not peritonitis” or “peritonitis”. In a prospective testing set (n=20) we demonstrated excellent performance for confirmation of infection in less than 1 hour (95% sensitivity, 100% specificity, 100% PPV, 90.9% NPV). We used our Flow cytometry-assisted Antimicrobial Susceptibility Test (FAST) to demonstrate prediction of quantitative antimicrobial susceptibility for 5 of the major microbial species causing peritonitis (Escherichia coli, Klebsiella spp., Pseudomonas spp., Staphylococcus aureus, and Staphylococcus epidermidis) with results in 3-4 hours. Across 23 antibiotics, and 260 individual minimum inhibitory concentration determinations, we demonstrated overall categoric agreement with conventional broth microdilution of 96.9%.
With the combined workflow, we demonstrate robust pre-clinical proof of concept of same-day confirmation of infection and antimicrobial susceptibility profiling by flow cytometry for PD peritonitis, with potential for adaptation to other types of serious infection.