Health officials link E. coli sickness to packaged spinach

Bad news for Popeye: an E. coli outbreak in eight states that so far has killed one person and sickened fifty has been traced to bagged spinach. Yesterday federal health officials warned consumers not to eat the leafy green until investigators had isolated the source. This is a good time for us to review a few technologies that might help control and prevent future E. coli outbreaks.

HEADLINE: New method for identifying bacteria in a hurry

Scientists from the National Cancer Institute (NCI) and National Institute of Standards and Technology (NIST) have developed a rapid method for detecting and identifying very small numbers of diverse bacteria, from anthrax to E. coli. The work is described in the 28 March issue of Proceedings of the National Academy of Sciences. The work could lead to the development of handheld devices for accelerated identification of biological weapons and antibiotic-resistant or virulent strains of bacteria, two situations in which speed is essential.

Unlike time-consuming traditional ways of identifying infectious bacteria, the new method speeds up the process by using fast-replicating viruses (called bacteriophages or phages) which infect specific bacteria of interest and are genetically engineered to bind to “quantum dots.” Quantum dots are nanoscale semiconductor particles which give off stronger and more intense signals than conventional fluorescent tags. They are also more stable when exposed to light. The method detects and identifies ten 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 with quantum dots that have different emission colors.

A provisional patent application was filed originally through NIST, and a non-provisional patent application was filed more recently through the National Institutes of Health, the parent agency of NCI. The NIST contributions to the work include experimental design and fluorescence imaging. Other authors are from NCI, NIH, SAIC-Frederick Inc., and the National Cancer Institute in Frederick, Maryland. The work was funded by the National Institute of Health (NIH), NCI, NIST, and the Center for Cancer Research.

-read more in this NIST news release

HEADLINE Scientists: Copper is safer than stainless steel in food processing

In the June issue of the Applied and Environmental Microbiology journal, researchers from the University of Southampton in the UK and the Copper Development Association in New York say that the use of cast copper alloy instead of stainless steal would help prevent cross contamination of E. coli during food processing. Escherichia coli O157 — the technical name for E. coli