Electrochemical Sensor-Based Detection of β-Lactamase-Mediated Ampicillin Resistance in Real-Field Isolates: High-Throughput Redox Assay

The widespread consumption of ampicillin, a commonly prescribed β-lactam antibiotic, has accelerated the emergence of multidrug-resistant bacteria and increased the persistence of antibiotic residues in the environment. However, antimicrobial resistance (AMR) surveillance is still constrained by conventional approaches that are not optimal for rapid field-level monitoring. In this study, a rapid electrochemical method was developed for the detection of ampicillin resistance genes (AmpRGs) in wastewater. Fast-scan cyclic voltammetry (FSCV) and differential pulse voltammetry (DPV) were employed to detect AmpRGs and assess their occurrence in four different real-field samples sourced from community drains, industrial wastewater, hospital inlet, and sewage treatment plant drain. The proposed method demonstrated high analytical sensitivity, achieving a limit of detection of 6 × 10–9 μmol, with a distinct electrochemical signature. Quantitative analysis revealed a strong linear relationship (r2 = 0.97) between redox currents and gene copy number, enabling a reliable estimation of AmpRG abundance. Among all matrices, hospital inlet wastewater exhibited the highest gene load (4.5 × 1013 copies), substantially exceeding levels observed in the synthetic gene library. Electrochemical findings were compared with molecular techniques, confirming accuracy and stability. This work provides a rapid and selective approach for wastewater-based AMR surveillance.