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  • A step closer to stopping E.coli

Photonics Spectra
Dec 2008
Amanda D. Francoeur,

WEST LAFAYETTE, Ind. – To prevent Escherichia coli from reaching consumers, scientists have developed a method of detecting and detaining one of its more common virulent strains, serotype O157:H7. This bacterium is found in contaminated foods such as beef, vegetables and unpasteurized milk and is estimated to infect more than 70,000 people a year. The technique could help food-processing companies track the E. coli’s source and even put an end altogether to outbreaks of food-borne illness.

Intelliphage, the company that developed the method, was co-founded by Dr. Bruce M. Applegate, an associate professor of food science at Purdue University and research associate Lynda Perry. The business has created a nonpathogenic virus that, when incorporated into food contaminated with E. coli, will bind to the strain and turn the food red or make it luminesce. The transformation will alert food processing companies that their product is unfit for human consumption and must be recalled.

Applegate genetically engineered the Enterobacteria phage T4 virus to target the pathogenic bacteria by growing it in a controlled environment within a nonpathogenic E. coli host. When introduced into food, the phage uses long tail fibers to identify the E. coli cell surface receptors. A signal is sent to the baseplate of the phage, which releases short tail fibers that connect permanently to the E. coli cell. Upon attachment, the baseplate changes, and the fibers induce glycoprotein V, which punctures the outer membrane of the E. coli. Once the cell wall and plasma membrane are broken down, DNA from the phage is transmitted into the cell.

Shown is 3-D visualization of genetically engineered Enterobacteria phage T4, which can detect and trap a virulent strain of E. coli that causes countless outbreaks of food-borne illness. The phage attaches to pathogenic cells and injects DNA to make contaminated food luminescent or red in color. Image created by Seyet LLC in collaboration with the Michael G. Rossmann laboratory at Purdue University. Funded by the National Science Foundation. An animated video of the process can be found at

Prior methods of confirming the presence of E. coli in food took more than 24 hours, but the new technique can detect the bacteria within four hours. In addition, it can identify one bacteria cell in only 25 grams of food, furthering its early detection capability. Injecting the T4 phage does not destroy the E. coli but instead detains it so that, when food companies make recalls, it is easy to track the contamination’s source.

Many laboratories grow the T4 phage in an E. coli host, which involves large quantities of the bacteria and potentially exposes the public to large amounts of it accidentally. Intelliphage, however, has devised a way to avoid this threat by growing the phage within a nonpathogenic strain.

Food processing companies can benefit from the method without spending money on additional equipment because, according to Applegate, most companies already are equipped with luminometers – highly sensitive photometers that measure low light levels from luminescent techniques.

The next step for researchers at Intelliphage is redeveloping the virus to target and contain the salmonella, listeria, staph and mycobacterium tuberculosis bacteria that are the more common contaminants in food.

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