Scientists developed a simple, rapid method for identifying food poisoning-inducing bacteria based on color differences in the scattered light of composite structures consisting of gold, silver, and copper nanoparticles and polymer particles. Using these composites as test labels bound to specific bacteria, the researchers detected food poisoning bacteria E. coli O26, E. coli O157, and S. aureus as white, red, and blue scattered light, respectively, under the microscope. This new method enables simultaneous identification of multiple bacterial species within one hour, significantly shortening the usual 48-hour time requirement for conventional bacterial tests.