Traditional ways of identifying infectious bacteria and their possible treatments can be time consuming and laborious, requiring the isolation and growth of the bacteria over many hours or even days. The new method speeds up the process by using fast-replicating viruses (called bacteriophages or phages) that infect specific bacteria of interest and are genetically engineered to bind to "quantum dots." Quantum dots are nanoscale semiconductor particles that give off stronger and more intense signals than conventional fluorescent tags and also are more stable when exposed to light. The method detects and identifies 10, or fewer, target bacterial cells per milliliter of sample in only about an hour.
The phages were genetically engineered to produce a specific protein on their surface. When these phages infect bacteria and reproduce, the bacteria burst and release many phage progeny attached to biotin (vitamin H), which is present in all living cells. The biotin-capped phages selectively attract specially treated quantum dots, which absorb light efficiently over a wide frequency range and re-emit it in a single color that depends on particle size. The resulting phage-quantum dot complexes can be detected and counted using microscopy, spectroscopy or flow cytometry, and the results used to identify the bacteria. The new method could be extended to identify multiple bacterial strains simultaneously by pairing different phages wit
Contact: Laura Ost
National Institute of Standards and Technology (NIST)