Because this outbreak and its cause were recognized quickly, the ground beef patties were recalled, and an estimated 800 illnesses were prevented. In collaboration with the Association of State and Territorial Public Health Laboratory Directors, CDC created PulseNet so that scientists at public health laboratories throughout the country could rapidly compare the PFGE patterns of bacteria isolated from ill persons and determine whether they are similar. Similar PFGE patterns suggest that the bacteria isolated from ill persons come from a common source, for example, a widely distributed contaminated food product. Strains isolated from food products by regulatory agencies can also be compared with those isolated from ill persons. Identifying these connections can help to detect outbreaks and remove contaminated foods from the marketplace.
Bacteria replicate themselves by dividing in two.
When a bacterium divides, the two daughter bacteria have the same genetic makeup as the parent bacterium, like identical twins. The DNA that has been cut in pieces is placed at one end of the gel. A pulsing electric field applied across the gel drives the DNA pieces across the gel over a period of hours. The smallest pieces slip through the sieve more quickly, so the pieces are separated as distinct bands on the gel. These laboratories will be able to submit new patterns to the national database online and obtain epidemiologic information associated with patterns in the database.