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Detection and quantification of pathogenic bacteria remain critical amidst the recent focus on viruses as bacterial contamination continues to contribute significantly to hospitalizations and fatalities globally. With rising antibiotic resistance exacerbating the challenge, simple and cost-effective approaches are needed for the prompt identification of pathogenic bacteria. Conventional methods, while effective, often entail time-consuming processes or require sophisticated equipment, limiting their utility in resource-limited settings. In this study, we employed impact electrochemical impedance spectroscopy (IEIS) for the rapid detection and counting of bacteria at exceptionally low concentrations. The technique measures changes in impedance spectra caused by the impact of the bacteria on electrode surfaces, providing a label-free detection method. We demonstrated the detection of two types of bacteria (Escherichia coli and Bacillus subtilis) using gold ultramicroelectrodes (Au-UME). We observed significant shifts in the impedance spectra corresponding to bacterial concentrations as low as 100 CFU/mL for E. coli and 1000 CFU/mL for B. subtilis. Our results show that the charge-transfer resistance (Rct) increases with the bacterial concentration, attributed to the blockage of redox probe oxidation at the Au-UME surface. This impedance change allows for the quantitative analysis of bacterial presence. The sensitivity and versatility of our method enhance bacterial detection, offering a significant advantage over traditional techniques. This study validates IEIS as a robust tool for detecting and counting bacteria, addressing contamination and infection control challenges. Further research in this area promises to advance this label-free, sensitive, and real-time detection technique.
Shukla et al. (Wed,) studied this question.