Accelerated electrochemical antibiotic susceptibility testing using disposable electrodes and Resazurin

Stenotrophomonas maltophilia and Shigella sonnei are increasingly associated with serious infections and shigellosis, respectively, with conventional antibiotic susceptibility tests requiring 18-24 h or more, often delaying treatment. In this study, we present a novel electrochemical sensor employing the redox indicator Resazurin for rapid assessment of antibiotic susceptibility. Detection of live S. maltophilia and S. sonnei was achieved within 2 h as Resazurin, reduced to Resorufin by metabolically active bacteria, produced a measurable decrease in the reduction current. Following exposure to antibiotics (levofloxacin, trimethoprim-sulfamethoxazole, and ampicillin), changes in Resazurin's reduction current were monitored using Differential Pulse Voltammetry. Susceptible bacteria exhibited minimal changes in current, while resistant strains actively reduced Resazurin, lowering the current. This sensor provided results within 4-5 h, aligning with traditional methods like disk diffusion and broth microdilution but with improved speed and operational simplicity. These findings highlight the potential of the developed sensor as a rapid, reliable alternative for antibiotic susceptibility testing.