PCR has revolutionised microbiology in food testing and clinical diagnosis since it was developed in 1983, allowing rapid identification of bacteria compared to conventional culture media. Its specificity is ideal when you know what you’re looking for, but what about when you have a clinical sample in which you’re not sure of the identity of the etiological agent? What diagnostic tools are out there able to identify - rapidly - the cause of an infection from an unpurified sample? Well, DNA chips may be the answer.
Image credit: Uwe Hermann, Flickr
A paper was published in Nature Communications last week, reporting the development of a chip able to identify pathogens from unpurified samples. The chip works by having connected biosensors containing peptide nucleic acid (PNA) probes which target a number of pathogenic organisms. When a target organism is present, the phosphate backbone of the bound DNA triggers an electrocatalytic current, signaling detection. The researchers developed probes targeting 90% of common urinary tract infection pathogens including antibiotic resistance markers. They were able to detect E. coli and its beta lactamase gene as well as Staphylococcus aureus in a mixed sample in a matter of minutes.
This technology is of a similar concept to microarrays; chips which detect DNA sequences, signaled by a fluorescent indicator. However, although microarrays are a mainstay tool in gene expression profiling, they have not proved as popular as other rapid methods such as PCR in the clinical diagnostic lab. This is partly due to the expensive fluorescence-based readout which requires high-tech, complicated algorithms for interpretation of results. What’s exciting about this advancement is that it is not only cheaper, but also easier for the user to decipher results, making it much more attainable for commercial use.
We’re currently in the most rapidly advancing era of microbiology, and this technology adds to the list of incredibly exciting advancements in this field, along with whole genomic sequencing and mass spectrometry. What do you think the future will hold? Do you think DNA chips in time will be the main diagnostic tool in clinical labs, or will mass spectrometry – already commercially available and continually developing – take hold instead?
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