CHICAGO • Investigations into foodborne illness are being radically transformed by whole genome sequencing, which US officials say is enabling them to identify the source of an outbreak far more quickly and prevent additional cases.

Previously, samples from sick patients were sent to state and federal labs, where disease detectives ran tests to see if the infections were caused by the same bug.

When enough matches emerged, typically a dozen or so, epidemiologists interviewed sick people, looking for a common food item that was causing the outbreak.

But the testing was not definitive, and finding links took time. "While all of this was going on, more contaminated products were getting out into the public," said Dr Steven Musser, deputy director for scientific operations at the US Food and Drug Administration's Centre for Food Safety and Applied Nutrition.

Now, the FDA is building a network of state and federal labs equipped to map out the exact DNA sequence of strains of listeria, salmonella and other food-borne pathogens found in sick patients. These sequences are then uploaded to a public database at the National Institutes of Health. The technology can not only differentiate a pathogen from multiple related species, but also show slight mutations within the same strain.

At the same time, the FDA has begun sequencing pathogens found during routine plant inspections and adding those to the database. One benefit of that, it says, is being able to quickly connect patients within an outbreak.

Another is the potential to identify the source of an outbreak after just a few patients fall ill, shortening the time it takes to get tainted food off store shelves. To increase the odds of a match, the FDA wants manufacturers to contribute samples of pathogens found during their own plant inspections.

But convincing companies to offer up potentially incriminating evidence has been a hard sell, according to interviews with public health officials, food manufacturers and experts on recalls.

"You catch things far earlier" with sequencing, said Dr David Lipman, director of the National Centre for Biotechnology Information. "It can be two cases. If you see a match, Bam! You've got 'em."

REUTERS