A portable microbiology testing kit was initially developed by Robert Metcalf, Professor Emeritus of Microbiology at California State University at Sacramento. He introduced this method to Susan Murcott in Kenya in 2005 and conducted training at MIT in June 2008. Murcott then modified the testing kit to also include a body belt incubator and other materials needed in order to perform and interpret the tests. The body belt incubator, which incubates water samples using body temperature alone, serves as a low-cost, portable, and convenient alternative to traditional laboratory incubators that are costly and require electricity. She also created several different model sizes of the product and branded it “EC-Kit.” Murcott introduced the technology to the Non-Governmental Organization (NGO) “A Single Drop,” and introduced the director of that NGO to Robert Metcalf, after which they brought the technology to the Philippines. It was included in the World Health Organization publication “Compendium of New and Emerging Health Technologies” as an emerging technology (WHO, 2011).
The EC-Kit contains two complementary tests for E.coli: the Colilert® 10-mL presence/absence (P/A) test, and PetrifilmTM test. The Colilert® test contains the same formulation as in the Quanti-Tray® tests, only it is reduced to its simplest form: a single P/A test of a 10-mL sample. However, the P/A. Colilert® test has a detection limit equivalent to 10 MPN/100 mL. In this Colilert® test, the substrate is hydrolyzed by the total coliform by-products, and reacts with a specific enzyme found in E.coli. A positive result is given by a yellow sample (presence of total coliforms), or a sample that fluoresces under long-wave UV illumination in the dark (presence of E.coli) after 24-hour incubation (Gerba, 2000). The PetrifilmTM test provides a quantitative count of total coliform bacteria colonies -- red colonies with gas bubbles after 24-hour incubation -- plus E.coli colonies --blue colonies with gas bubbles after 24-hour incubation -- with a 1-mL sample volume.
Colilert® can test both chlorinated and non-chlorinated samples. However, chlorinated samples should first be treated with sodium thiosulfate before the Colilert® reagent is added. On the other hand, the Petrifilm™ cannot be used to test chlorinated samples.
The EC-Kit is simple, low-cost and easy-to-use. The most promising features of the EC-Kit are that it can be used by virtually anyone who receives the brief 15 minute training, and bacterial incubation is performed using the body-belt incubator, so it is completely portable.
EC-Kit v1.0 including body belt incubator (left). Pamela Silva, (MIT Mechanical Engineering, ’12) modelling the EC-Kit’s body-belt incubator in San Juan, Puerto Rico, following a week of EC-Kit trainings and testing of drinking water quality in various communities affected by Hurricane Maria (right).