Application of bacteriophage to develop indicator for Escherichia coli detection and modulation of its biochemical reaction to improve detection ability: A proof-of-concept study

Abstract

Bacteria indicators have been widely developed but still need complicated techniques, instruments, or well-trained users. This is a proof-of-concept study to develop a straightforward and colorimetric bacterial indicator using bacteriophages (phages) as bio-receptors and simple biochemical reactions for high sensitivity. Among the various phages, phage T4 with a high specificity to Escherichia coli was used. Hydrophilic polyvinyl alcohol and trehalose were used as matrix polymers, and the optimal formulation ratio was examined to enhance the phage stability in the indicator matrix. Its sensitivity and detection rate were improved by investigating the interactions between phage T4 and isopropyl β-d-thiogalactopyranoside. The final indicator showed high sensitivity detecting up to 10 CFU/mL after 11 h, even in the food application test such as drinking water and milk samples containing different fat contents. Although some challenges remain to satisfy the regulatory requirements for bacteria in foods and be applied to various foods, the introduced simple approach can pave the way to develop indicators to detect E. coli present in real food using phages.