DNA ‘Fingerprint’ Techniques Can Aid Food Safety

Tracking polluted water back to the source of its contamination can help researchers assess potential health risks and determine methods for cleaning up the affected water. Now those same techniques can be utilized to keep food safe.

For about a decade, researchers have used a technique called microbial source tracking to trace water pollution back to its source. One of those researchers, Dr. Alexandria Graves, a soil scientist at NC State, collects genetic libraries of varieties of bacterial pathogens like E. coli from water samples and then cracks their DNA code to look for similar genetic “fingerprints” in the environment. In an admittedly simple example, if specific genetic fingerprints in an E. coli sample from polluted water downstream from a hog lagoon match those in or near the lagoon, that evidence can point the finger at the lagoon as the source.

Similarly, researchers are also trying to track the sources of the harmful pathogens that can contaminate food and cause illness – common microbes like E. coli, Salmonella and Enterococcus faecium, many of which are already resistant to antibiotics and are increasingly resistant to food-preservation measures. Food-borne diseases are responsible for an estimated 76 million illnesses and 5,000 deaths each year in the United States, according to estimates published in 1999.

Graves says that the same microbial source tracing techniques that she uses for water-quality studies can also be effectively used for food safety. Matching the genetic fingerprints of a particular pathogen with those in a contaminated source in the food chain – back to the restaurant, kitchen or market, further back to the processing facility and even further back to the field or farm or origin – can provide clues to where and how the contamination occurred. It can also highlight where safe practices may be lacking in the food chain.

Graves wrote a chapter, titled “Food Safety and Implications for Microbial Source Tracking,” in a recently published book – “Microbial Source Tracking: Methods, Applications and Case Studies” – that shows how genetics used in microbial source tracking can assist in tracking food-borne pathogens to their source.