Low-cost, real-time detection of bacterial growth via diffraction-based sensing.

The emergence of antibacterial resistance impacts healthcare networks globally, with mortality rates and linked burdens of infection disproportionately affecting the developing world. Rapid alternatives to antibiotic susceptibility testing (AST) allow for swifter, more effective treatment, though they are limited in use in low-resource settings due to significant cost barriers. Herein we demonstrate a simple, cost-effective diffraction sensing-based approach for rapidly detecting bacterial growth (a precursor to AST). Diffraction gratings (1D, lined) directly comprised of our test bacteria (Escherichia coli DH5α) were produced using soft agar-based gel templates designed to direct bacterial attachment and produce a near-zero background signal. The diffraction spot intensities from the live bacterial gratings were monitored in growth and no growth (ampicillin) conditions at room temperature, using a simple fixed laser and photodetector setup. Growth-induced differences in signal were observed within 10-20 minutes, highlighting the sensitivity of this approach and its potential to be adapted as a rapid and accessible AST alternative.