Label-free electrical sensing of bacteria in eye wash samples: A step towards point-of-care detection of pathogens in patients with infectious keratitis.

The diagnosis of keratitis is based on visual exam, tissue cytology, and standard microbial culturing to determine the type of the infectious pathogen. To prescribe appropriate therapy, it is important to distinguish between bacterial, fungal, and viral keratitis, as the treatments are quite different. Diagnosis of the causative organism has a substantial prognostic importance. Further, timely knowledge of the nature of the pathogen is also critical to adapt therapy in patients unresponsive to empiric treatment options, which occurs in 10% of all cases. Currently, the identification of the nature of the pathogen that causes keratitis is achieved via microbial culture screening, which is laboratory-based, expensive, and time-consuming. The most frequent pathogens that cause the corneal ulcers are P. aeruginosa and S. aureus. Here, we report a microchip for rapid (<1h) detection of P. aeruginosa (6294), S. aureus(LAC), through on-chip electrical sensing of bacterial lysate. We evaluated the microchip with spiked samples of PBS with bacteria concentration between 101 to 108 CFU/mL. The least diluted bacteria concentration in bacteria-spiked samples with statistically significant impedance change was 10 CFU/mL. We further validated our assay by comparing our microchip results with the standard culture-based methods using eye washes obtained from 13 infected mice.