In recent years, uncovering and tracking foodborne outbreaks involving bacterial pathogens has become vastly easier with PulseNet. The following is from the CDC PulseNet site:
PulseNet is a national network of public health and food regulatory agency laboratories coordinated by the Centers for Disease Control and Prevention (CDC). The network consists of: state health departments, local health departments, and federal agencies (CDC, USDA/FSIS, FDA).PulseNet participants perform standardized molecular subtyping (or “fingerprinting”) of foodborne disease-causing bacteria by pulsed-field gel electrophoresis (PFGE). PFGE can be used to distinguish strains of organisms such as Escherichia coli O157:H7, Salmonella, Shigella, Listeria, or Campylobacter at the DNA level. DNA “fingerprints,” or patterns, are submitted electronically to a dynamic database at the CDC. These databases are available on-demand to participants—this allows for rapid comparison of the patterns.
Pulsed Field Gel Electrophoresis (PFGE) is a methodology that digests bacterial DNA into fragments which can be run on gels, which produces unique patterns. Like human fingerprints, each bacteria and its offspring have a unique PFGE pattern. If two bacteria are found with an indistinguishable pattern, it is likely that they have a common source and may be part of an outbreak.
A national computer database of PFGE patterns is housed at CDC. States submit PFGE patterns of pathogens that have made people sick to the database over the Internet. The computer then automatically scans previously submitted patterns searching for matches, i.e., indistinguishable DNA fingerprint patterns of pathogens 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.
PulseNet is an invaluable resource that identifies outbreaks that would have most likely gone unnoticed. In the 2006 E. coli outbreak linked to bagged, fresh spinach, state epidemiologists uncovered the outbreak using PulseNet technology and quickly alerted the CDC. Within a short period of time, the FDA issued a warning regarding fresh, bagged spinach that may have prevented many more illnesses and deaths.
