Editorial Feature

Bio-Sensing Dipstick Test for E. Coli in Water

The bacterium Escherichia coli, or E. coli, encompasses several hundreds of strains, all of which are often associated with causing both foodborne and waterborne illnesses.

While most E. coli strains are present in normal amounts with the intestines of both healthy humans and animals, the production of Shiga toxin by certain strains of E. coli can cause gastrointestinal symptoms of stomach cramps, diarrhea and vomiting when the toxin infects an individual1. To prevent the spread of E. coli infections, individuals must wash their hands regularly, only eat pasteurized dairy products and juices, eat meat that has been thoroughly cooked and avoid swallowing water while swimming.

Although these methods may seem sufficient enough in reducing an individual’s susceptibility to E. coli, water sources such as lakes, pools and other supplies that have been contaminated with human or animal feces remain a prevalent source of E. coli. This is especially true for undeveloped areas of the world that may not have access to stringent water purification systems, thereby leaving people of these impoverished nations at a even greater risk to such harmful illnesses.

Water quality tests that are used by the U.S. Environmental Protection Agency are conducted to monitor any possible traces of E. coli in water supplies, however such sterile procedures often require expensive equipment and a minimum of five days to conduct the complete testing. Similarly, field kits can be purchased by trained individuals, however they remain a highly expensive option that is limited in its ability to only be fully conducted in a lab setting.

To combat such challenges in the analytical testing aspect of E. coli infections, a group of Researchers led by Dr. Naga Siva Kumar Gunda at the Waterloo Institute for Nanotechnology have constructed a new litmus paper test to detect for the presence of E. coli in water samples2. That paper test, otherwise known as a DipTest, is composed of three different sections that include a wax hydrophobic barrier which is immediately above a reaction zone that is coated with enzymatic substrates and other formulated chemical reagents, followed by a D-glucose-coated area of attraction.

If E. coli is present within a given water sample, it is attracted towards the D-glucose area as a result of a chemotaxic mechanism. The water will then continue towards the top of the paper strip through a capillary motion and will stop when it reaches the hydrophobic barrier. The reaction zone will produce a pinkish-red color to confirm the presence of E. coli contamination within a sample.

Such bio-sensing testing methods have been successful in previous attempts to quantify or detect the presence of biomolecules in a particular sample, thereby allowing for both a low-cost and rapid method of detection. The use of antibody-coated immune-magnetic nanoparticles was successfully incorporated to test for the presence of bacteria in water samples in an early study conducted by Hossain et. al3.

The work conducted by Gunda’s group is a realistic step towards the manufacturing of a DipTest device that can be used for field deployable water testing, which will determine within minutes whether the given water sample is contaminated with E. coli bacteria or not.

Aside from being used in remote locations that may not have the immediate access to high tech testing procedures such as those conducted by the EPA, such as swimming pools, lakes, rivers and beaches, such a DipTest device could be a revolutionary tool in impoverished areas of the world that have never previously had access to a clean water supply.

By understanding the threat of a possible spread of E. coli infection within a certain water supply, Health Professionals can offer immediate assistance to those who are already affected, as well as provide the required information for individuals of the area to prevent their own susceptibility to such infection.

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  1. “E. Coli Outbreaks Fast Facts” – CNN
  2. “DipTest: A litmus test for E. coli detection in water” N. Gunda, S. Dasgupta, et al. PLOS. (2017). DOI: 10.1371/journal.pone.0183234.
  3. “Multiplexed paper test strip for quantitative bacterial detection” Hossain S.Z., Ozimok C., et al. Analytical and Bioanalytical Chemistry. (2012). DOI: 10.1007/S00216-012-5975-x.

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Benedette Cuffari

Written by

Benedette Cuffari

After completing her Bachelor of Science in Toxicology with two minors in Spanish and Chemistry in 2016, Benedette continued her studies to complete her Master of Science in Toxicology in May of 2018. During graduate school, Benedette investigated the dermatotoxicity of mechlorethamine and bendamustine; two nitrogen mustard alkylating agents that are used in anticancer therapy.


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