PFGE Testing for E. coli
Pulsed-field gel electrophoresis (PFGE) is the DNA “fingerprinting” method that scientists use to determine the source of an E. coli outbreak. The DNA of E. coli found in outbreak victims, in food and environmental samples is digested into pieces with enzymes that are able to specifically break the DNA molecule into individual pieces. The digested DNA is placed at one end of the gel. A pulsing electric field applied across the gel drives the DNA pieces into the gel over a period of hours. The smallest pieces slip through the pores of the gel more quickly, so the pieces are separated as distinct bands in the gel, based on size. The resulting pattern of 30 to 50 bands, which resembles a bar code is the DNA “fingerprint.” This DNA fingerprint is referred to as the PFGE pattern.
Like human fingerprints, each E. coli bacterium and its offspring have a unique PFGE pattern. If two bacterium are found with an indistinguishable pattern, it is likely that they have a common source and are part of the same E. coli outbreak. A national computer database of PFGE patterns is housed at CDC as part of PulseNet. Health investigators throughout the country submit PFGE patterns of E. coli O157:H7 and pathogens that have made people sick to the database. The computer then automatically scans previously submitted patterns searching for matches, i.e., indistinguishable DNA fingerprint patterns of E. coli bacterium that have made other people sick. If a match is found, a signal is given to the submitter that duplicate patterns are present and where they came from, so that an investigation can begin to look for a common source.
If PFGE patterns match, it suggests that various unrelated individuals may have been infected by a common source. If the PFGE pattern of a food product matches the PFGE patterns of those sickened in an outbreak, it is highly likely that the food product is the source of the outbreak. Matching PFGE patterns are an important part of proving “causation” in an E. coli case seeking money damages.
Anyone diagnosed with an E. coli infection, should contact our law firm about PFGE testing.
