Colorimetric and Electrochemical Detection of Escherichia coli and Antibiotic Resistance Based on a p-Benzoquinone-Mediated Bioassay.

The facile and economical identification of pathogenic bacteria, especially their antibiotic-resistance, is crucial in the realm of human health and safety. The presence of Escherichia coli ( E. coli) is considered as an indicator of water contamination and is closely related to human health. Herein, inspired by the biocatalysis of bacterial surfaces, we developed a simple and cost-effective colorimetric- and electrochemical-based bioassay that is capable of analyzing both the presence of E. coli and its relative level of antibiotic resistance. In this approach, p-benzoquinone is used as a redox mediator to monitor the bacterial concentration and specifically distinguish E. coli from four other common clinical bacteria, namely, Staphylococcus aureus ( S. aureus), Enterococcus faecalis ( E. faecalis), Salmonella pullorum ( S. pullorum), and Streptococcus mutans ( S. mutans). A visible color change, captured with a smartphone using a "light box", without relying on any complex instruments, can reflect the concentration of bacteria. The accurate quantification of E. coli was investigated with an electrochemical system in the concentration ranges of 1.0 × 103 to 1.0 × 109 CFU/mL. We further demonstrated the capability of the presented biosensor in identifying drug-resistant bacteria with two artificially induced antibiotic-resistant bacteria. Therefore, the presented bioassay is not only capable of detecting E. coli with high sensitivity and specificity but also provides a rapid solution to evaluate E. coli antibiotic resistance.