Litmus paper, long known as a low-tech method of testing substances for acidity, might have a new use as a cheap, quick way to test for E. coli, according to researchers at McMaster University in Ontario. The researchers correlated levels of E. coli bacteria with pH values represented by the colors to which the litmus paper changes. The work has been led by Dr. Yingfu Li of McMaster’s Sentinel Bioactive Paper Network, which has a goal of finding innovative uses for paper. The researchers say that the test, which costs just a few cents, can be easily used by homeowners to test private wells or swimming pools and see the results within hours. If the paper changes color, there are bacteria present. Compare that to the current standard test for homeowners, which requires a sterile testing kit supplied by a local health authority, with the test results coming later by mail. Even public health agencies currently need laboratory personnel to perform tests of lakes and beaches for E. coli and other bacteria. If the litmus paper test shows promise outside the research environment, it could significantly hasten testing of public waters. The research team is now looking at testing methods for other food- and water-borne bacteria, including Listeria and Salmonella. They have also received a grant to develop a similar test for colorectal cancer. Just this week, a possible case of E. coli was reported in the Seattle suburb of Mercer Island after E. coli was detected in the municipal water system and residents were placed on a boil-water alert. Above: Litmus test results using apple juice, milk and lake water as real-life samples, along with clean water as a negative control (NC).