The process of obtaining the DNA “fingerprint” is called Pulse Field Gel Electrophoresis (PFGE).  The PFGE technique is used to separate the DNA of the bacterial isolate into smaller pieces. The DNA is placed in a flat gel matrix of agarose, a polysaccharide obtained from agar, and exposed to an alternating electric field. [52, 53] Individual pieces of DNA, or bands, will migrate across the gel, creating a bar code-like pattern unique to each strain.  By performing the procedure, scientists can identify hundreds of strains of E. coli O157:H7 as well as strains of Listeria, Salmonella , and Campylobacter.