In 2010, the World Health Organization reported that foodborne pathogens caused over 600 million illnesses and over 400,000 deaths in that year alone.1 Because of this, it is important to be able to detect these types of pathogens to prevent outbreaks from occurring. Most of the common bacterial detection methods require a centralized laboratory, trained personnel, and a significant amount of time to process results. As an accessible alternative to traditional methods, scientists have been looking towards paper-based analytical devices in recent years to circumvent these problems. Because of its porous nature, paper can absorb, dry and store chemicals deposited on it. It can induce flow via capillary action without the need for instrumentation. Earlier in 2019, the Kwon group from Seoul National University of Science and Technology utilized these properties to design a device for the detection of two E. coli strains in milk samples.2 With a single sample addition step, fluid flows vertically through various layers of paper containing a detergent to lyse bacteria, and oxidizing layer to adjust pH, and a substrate layer. One substrate, X-β-gluc, reacts with β-glucuronidase to produce a light blue color, and the other, S-β-gal, reacts with β-glucuronidase making a magenta color. While nearly all strains of E. coli contain both enzymes, E. coli O157:H7 (a toxin producing pathogen), only contains β-galactosidase. Therefore, in the presence of E. coli O157:H7, the device will result in a magenta hue; whereas, nearly any other strain would result in a blue/magenta combination. The authors of the paper were able to distinguish between toxic and non-toxic strains of E. coli on the device and quantify both strains with an LOD of 101 CFU/mL after a 5 hour enrichment.
- Havelaar, A. H.; Kirk, M. D.; Torgerson, P. R.; Gibb, H. J.; Hald, T.; Lake, R. J.; Praet, N.; Bellinger, D. C.; de Silva, N. R.; Gargouri, N.; Speybroeck, N.; Cawthorne, A.; Mathers, C.; Stein, C.; Angulo, F. J.; Devleesschauwer, B.; on behalf of World Health Organization Foodborne Disease Burden Epidemiology Reference, G., World Health Organization Global Estimates and Regional Comparisons of the Burden of Foodborne Disease in 2010. PLoS Med 2015, 12 (12), e1001923.
- Kim, H. J.; Kwon, C.; Noh, H., Paper-Based Diagnostic System Facilitating Escherichia coli Assessments by Duplex Coloration. ACS Sensors 2019, 4 (9), 2435-2441.