A team of biochemists and engineers at McMaster University has developed a new test for detecting bacteria in fluids, thereby making it as simple as observing a color change to confirm the presence of disease-causing pathogens.

With the promise of easier diagnostic tests and greater food safety, the biogel test can reportedly be employed by untrained users to confirm contamination in fluids — like lake water, urine or milk, for instance — by changing color in the presence of bacteria, such as E. coli and listeria, among others.

Source: Advanced Materials (2024). DOI: 10.1002/adma.202411173

To accomplish this, the test uses harmless bacteriophages — which are the most common forms of life on Earth, each of which is specialized to destroy one form of bacteria — embedded within the gel to identify target bacteria in a sample of fluid, even in low concentrations.

During trials, the bacteriophages located and attacked the target bacteria in a sample, thus forcing the bacteria to release microscopic amounts of intracellular material that can be read by the biogel test. This interaction, according to the researchers, triggered a visible color change. Conversely, if the fluid in the sample is clean, the color is unchanged.

The researchers, who noted that the new process takes just hours and produces results more quickly than lab cultures, explained: "We've been using phages' destructive power to kill bacteria and resolve infections for years. Here, we're channeling that power in another way. Because phages can burst bacteria open, they can give us quick access to the biological components of those bacteria that we use to confirm their presence."

The test, described in the paper, "Bacteriophage‐Activated DNAzyme Hydrogels Combined with Machine Learning Enable Point‐of‐Use Colorimetric Detection of Escherichia coli,” was published in the journal Advanced Materials.