Single Step Electrochemical Biosensing Approach for the Detection and Discrimination of Beta‐Lactam Antibiotic Susceptibility

A label‐free electrochemical biosensing strategy was developed to detect and discriminate β‐lactamase susceptibility in Escherichia coli ( E. coli ) using a β‐lactam antibiotic cefotaxime (CTX) modified gold screen‐printed electrodes (AuSPEs). Clinically acquired E. coli isolates that producing extended spectrum β‐lactamases (ESBLs), both susceptible and resistant to CTX were employed as analytes. The biosensor performance was evaluated by electrochemical impedance spectroscopy (EIS), monitoring charge transfer resistance (Rct) values. Interaction between CTX and susceptible E. coli strains led to an increase in Rct, reflecting slower electron transfer due to strong antibiotic–bacteria interaction. In contrast, resistant E. coli strains produced β‐lactamase enzymes that hydrolyzed the β‐lactam ring of CTX, thereby hindering this interaction. Selectivity was assessed using Staphylococcus aureus ( S. aureus ) and Pseudomonas aeruginosa ( P. aeruginosa ) isolates, as well as a non‐β lactam antibiotic, vancomycin (VAN), as an alternative biorecognotion element. The biosensor demonstrated high sensitivity toward susceptible E. coli strains, achieving a limit of detection (LOD) of 6×10 2 CFU/mL. These results indicate that the proposed label‐free biosensor enables effective discrimination of β‐lactamase susceptibility and resistance in E. coli .