Weihong Tan and his colleagues at the University of Florida attached antibodies specific to the E. coli strain that causes food poisoning, O157:H7, to silica particles measuring just 60 nanometers across. The tiny particles also contained a few thousand fluorescent dye molecules. When the team mixed the particles into ground beef samples, the antibodies attached the silica to the bacteria. The signal given off by the dye allowed the scientists to detect a single bacterium in a sample in less than 20 minutes.
The new approach can be tailored to detect a variety of bacterial pathogens by changing the antibodies employed, according to a report published online this week by the Proceedings of the National Academy of Sciences. Indeed, the authors contend that the technique may emerge as a revolutionary tool for ultrasensitive detection of disease markers and infectious agents.