Polystyrene beads 1 μm

Uropathogenic E. coli ATCC25922 was purchased from American Type Culture Collection (ATCC) and stored at −80 °C in 5% glycerol. E. coli cells were cultured overnight for approximately 16 h at 35 °C in lysogeny broth (LB) and then for additional ~2 h at 16 °C to an OD₆₀₀ of ~0.7, corresponding to 5–6 × 10⁸ cfu/mL. E. coli cells were then collected by centrifugation and resuspended in phosphate-buffered saline to appropriate cell concentrations. Polystyrene beads (1 μm) were purchased from Bangs Laboratories, Inc (Fishers, IN, USA) and suspended in phosphate-buffered saline. Pooled healthy human urine (Lot number: BRH1311635) purchased from BioIVT (Westbury, NY, USA) was filtered using 5 μm syringe filters and then diluted 1:10. Samples were diluted until fewer than 1000 particles were counted with the particle localization algorithm, resulting in a concentration of approximately 10⁵ particles/mL.