University of Illinois at Urbana-Champaign researchers are using color changing pigments to identify infectious bacteria by their smell. Well practiced microbiologists with trained noses are known to be able to do that for some bacteria, so the researchers decided to adapt their technology to look for the byproducts of bacterial metabolism that are responsible for different scents.
The researchers spread blood samples on Petri dishes of a standard growth gel, attached an array to the inside of the lid of each dish, then inverted the dishes onto an ordinary flatbed scanner. Every 30 minutes, they scanned the arrays and recorded the color changes in each dot. The pattern of color change over time is unique to each bacterium.
"The progression of the pattern change is part of the diagnosis of which bacteria it is," Suslick said. "It’s like time-lapse photography. You’re not looking just at a single frame, you’re looking at the motion of the frames over time."
In only a few hours, the array not only confirms the presence of bacteria, but identifies a specific species and strain. It even can recognize antibiotic resistance – a key factor in treatment decisions.
In the paper, the researchers showed that they could identify 10 of the most common disease-causing bacteria, including the hard-to-kill hospital infection methicillin-resistant Staphylococcus aureus (MRSA), with 98.8 percent accuracy. However, Suslick believes the array could be used to diagnose a much wider variety of infections.
Next, the team is working on integrating the arrays with vials of liquid growth medium, which is a faster culturing agent and more common in clinical practice than Petri dishes. They have also improved the pigments to be more stable, more sensitive and easier to print. The device company iSense, which Suslick co-founded, is commercializing the array technology for clinical use.
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Abstract in Journal of The American Chemical Society: Rapid Identification of Bacteria with a Disposable Colorimetric Sensing Array
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