Could that omnipresent tool of high school chemistry labs—litmus paper, which indicates if a liquid solution is acidic or basic—be harnessed as perhaps the simplest assay yet for foodborne pathogens?
According to new research from Canadian scientists that recently garnered a prestigious “VIP Paper” award from the journal Angewandte Chemie, the answer is yes. Yingfu Li, PhD, and colleagues at McMaster University’s Sentinel Bioactive Paper Network were able to correlate levels of E. coli bacteria with pH values represented by the changing color of the litmus paper.
When testing apple juice, milk, and lake water, the E. coli-contaminated samples turned orange within 15 minutes and a shocking fuchsia by the end of an hour. It’s a simple test that requires no special training and costs only a few cents.
The scientists used a bacteria-specific RNA-cleaving DNAzyme probe as the molecular recognition element, and took advantage of the ability of urease to hydrolyze urea and elevate the pH value of the test solution.
Dr. Li says that the method should be adaptable to most food products. “It does need an aqueous solution to function, but, for example, you can puree vegetables or fruits to get such a solution.” The team is now in the process of testing the method’s validity for detecting Salmonella the DNA molecules, and just need to adapt the test for those two pathogens; we’re probably 50 to 60 percent of the way there at this point.”
Watch Dr. Li explain how he and colleagues are reinventing pH paper to detect pathogens.