What if testing for bacteria in fluids was a fast and easy as detecting viruses with a rapid antigen test? Researchers at McMaster University have come up with a novel test for detecting bacteria in a fluid sample that is easy to use, doesn’t require special equipment, and identifies specific species of bacteria in a matter of hours rather than days, outside of a lab setting and without the need to culture the sample for detection.

The test consists of a hydrogel containing a DNA indicator which changes colour in response to specific genetic sequences. During initial tests, there wasn’t enough bacterial DNA floating freely in the sample for the indicator to react with, and the colour change was minimal. Without culturing the bacteria to increase the concentration, the test wasn’t sensitive enough to be practical in the field. So, to avoid the need for a culturing step, the team added bacteriophages to the mix. Bacteriophages are viruses that target an individual strain of bacteria and – in the case of lytic bacteriophages – can cause the bacterial cell wall to rupture, killing the bacteria and releasing its intracellular material. This increases the concentration of bacterial DNA for the indicator to react with, and therefore increases the sensitivity of the test. The final sensitivity of the test when read with the naked eye was 101 CFU mL-1. If the bacteria being tested for aren’t present, the gel’s colour remains the same.
In areas of Canada and the rest of the world where access to clean drinking water is limited or unreliable, tests like these could make a difference. Rural areas often struggle with access to testing, prompting efforts such as a program at UBC which uses drones to deliver medical supplies and tests to compliment virtual care in areas where access to medical facilities is limited or non-existent. While a laboratory setting may always be the best place to confidently identify contaminants, a simple at-home test like the one developed at McMaster University could potentially be a quick and easy way to identify water that is not safe to drink or foods that are not safe to eat because of bacterial contamination.