Abstract: Urinary tract infections (UTIs) are among the most common bacterial infections worldwide and they predominantly affect women (~4x more likely than men). The antibiotic therapy of acute cystitis is based on clinical symptoms and the urine dipstick test result. Although rapid and simple, this test lacks specificity and sensitivity. It cannot detect Staphylococcus saprophyticus, the second major cause of cystitis in young women, after Escherichia coli, that is naturally resistant to the first line antibiotic. On the other hand, E. coli needs to count at least 105 bact./mL of urine to be detected. A more reliable diagnostic tool performed directly at the doctor’s office would help to improve UTI diagnosis and to better adapt the antibiotic therapy. With this work, we aimed to contribute to the improvement of urinary infection diagnostics by introducing a biosensor applying novel High Contrast Plasmonic imaging. The technique allows to specifically detect the targeted biological particle with specific ligand and to individually visualise and count them on a large field of view without labelling or complex instrumentation. The technique offers multiplexity aspect, meaning in one testing several targets can be simultaneously detected (human cells and bacteria) or different capture probes can be immobilised on the same surface to cover several uropathogens, broadening the applicability of the assay to clinical urine samples. A successful specific detection is demonstrated after a 5min incubation of the biosensor with a few tenths of microliters of unprocessed clinical urine sample infected by E. coli (CHUGA).
This work was supported by the Fondation pour la Recherche Médicale, grant number [ECO202306017339] to Vitas J.​​​​​

​​Direction
Thierry LIVACHE
Co-Direction
Yvan CASPAR – IBS and CHUGA
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