New Technology Can Diagnose Infections in Minutes

The detection and identification of bacteria currently rely on enrichment steps such as bacterial culture and nucleic acid amplification to increase the concentration of target analytes. These steps increase assay time, cost and complexity, making it difficult to realize a truly rapid point-of-care test.

Existing practice typically requires sending samples to laboratories to be cultured, a process that can take days. Providing immediate results to patients can reduce the spread of infection, improve patients' quality of life and simplify the work of busy clinicians. A new technology can distinguish strains of the same bacteria that can be treated with antibiotics from others that are resistant to antibiotics, a critical distinction that can help battle the growing problem of antimicrobial resistance, or AMR.

Biomedical Scientists at the McMaster University (Hamilton, ON, Canada) and their associates developed an electrical assay that uses electroactive RNA-cleaving DNAzymes (e-RCDs) to identify specific bacterial targets and subsequently release a DNA barcode for transducing a signal onto an electrical chip. Integrating e-RCDs into a two-channel electrical chip with nanostructured electrodes provides the analytical sensitivity and specificity needed for clinical analysis.

The microchip analyzes a droplet of bodily fluid such as blood, urine or saliva, using molecules that can detect the specific protein signature of an infection. The device, about the size of a USB stick, plugs into a smartphone, which displays the result. The e-RCD assay is capable of detecting 10 CFU (equivalent to 1,000 CFU mL^-1) of Escherichia coli selectively from a panel containing multiple non-specific bacterial species. Clinical evaluation of this assay using 41 patient urine samples demonstrated a diagnostic sensitivity of 100% and specificity of 78% at an analysis time of less than one hour compared with the several hours needed for currently used culture-based methods.

Yingfu Li, PhD, a Professor of Biochemistry and a senior author of the study, said, “This technology is very versatile and we're getting very close to using the same technology for COVID-19 testing. As scientists, we want to enable things. We are knowledgeable in different scientific and engineering principles, and when you put them together to help people, that is a special feeling. Having the chance to impact society is the reason we all do this work.” The study was published on June 24, 2021 in the journal Nature Chemistry.

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