A test based on a genetically modified bacteriophage has been developed in the United States for the rapid detection of pathogenic E. coli in water. Such tests are essential for preventing the spread of intestinal infections.

This year, more than 200 people in the United States have fallen victim to the pathogenic E. coli O157:H7 strain, five of whom died. The source of the E. coli was romaine lettuce ( Lactuca scariola longifolia ) from Arizona, which acquired the pathogen from contaminated irrigation water.

The law requires farmers to submit irrigation water samples to certified laboratories for safety testing. However, these tests typically take 1-2 days.

Recently, a team of researchers from the University of Iowa and Global Good/Intellectual Ventures developed a sensitive test to detect one specific strain of E. coli in water in 3 hours*.

A reporter gene encoding the luciferase enzyme was inserted into the T7NLC bacteriophage, which specifically recognizes and destroys a pathogenic strain of E. coli. When the phage entered the bacterium, the gene began to be expressed, and its product, the luciferase enzyme, began to glow. This glow can be used to determine whether the specific strain of E. coli is present in the solution. The scientists attached a special "block" to the enzyme that can bind to cellulose to facilitate its detection.

When scientists added a genetically modified bacteriophage along with cellulose granules to water contaminated with E. coli , the phages infected the bacteria. After the phage proteins were expressed and new phage particles were formed, the bacterial cell was destroyed, and the luciferase enzyme was released into the solution, where, thanks to the aforementioned "block," it "stuck" to the cellulose granules. Ninety minutes after mixing the phages with the samples, the scientists determined the amount of synthesized enzyme. This approach allows for rapid (less than 3 hours) detection of E. coli even at very low concentrations—less than 10 colony-forming units per 100 µl. All previous bacteriophage-based test systems required significantly longer analysis times.

Bacteriophages are agents that are safe for humans and, due to their high specificity, are promising means for the rapid detection of bacteria in various environments.

* Hinkley TC, Garing S, Singh S, Le Ny A-LM et al. Reporter bacteriophage T7NLC utilizes a novel NanoLuc:: CBM fusion for the ultrasensitive detection of Escherichia coli in water // Analyst, 2018,143: 4074-4082 . DOI:10.1039/C8AN00781K