An Amplification-Free Electrochemical CRISPR/Cas Biosensor for Drug-Resistant Bacteria

As the evolution of resistant microbes continues, there is a growing need for understanding and quickly classifying the resistances of various bacteria, especially during infection. Antimicrobial resistance (AMR) is one of the most pressing global health issues, with the World Health Organization (WHO) estimating that three hundred and fifty million deaths could be caused by AMR by 2050. Rapid diagnostic technologies can assist in addressing AMR by clarifying which microbe is invading and what its current AMR status is.

Towards this goal, Akkapol Suea-Ngam and colleagues in the deMello Lab at ETH Zurich have designed a sensor system to categorize drug resistant microbes. Their sensor system focuses on Methicillin-resistant Staphylococcus Aureus (MRSA). Due to MRSA’s hazard and ubiquity, a rapid, accurate and low-tech test is desperately needed. Importantly, the developed test does not involve amplification, but rather a highly sensitive CRIPSR driven electrochemical detection scheme. The presence of MRSA target DNA, and subsequent cis-cleavage, initiates collateral cleavage activity from CAS12a. This cleavage of ssDNA, off the electrode is then used to report the presence of MRSA target DNA. An impressive detection limit of 3.5 fM was shown and found to be linear over a broad range of target concentrations. It should be noted a 30% difference in signal was exhibited between positive and negative MRSA samples. Furthermore, the sensing system was tested on human serum samples containing MRSA and illustrated similar results to spiked buffer samples. Finally, and despite its simplicity, the novel electrochemical system offers performance metrics equivalent to standard PCR-based assays.

Written by Jake Lesinski

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