Food Protection Trends - March 2009 - 144

“perspectives” from your president s I write this column, state and federal public health authorities have identified peanut butter as the source for Salmonella in another widespread food poisoning outbreak. In the last two years, in North America, there have been numerous outbreaks including large ones involving leafy greens (several times), peanut butter (twice), peppers/ tomatoes, frozen potpies, and deli meats. Consumer groups and individual consumers are asking the question, is our food supply less safe today than in the past? It is my belief that our food supply is as safe or safer today than in previous years. The meat industry has made tremendous strides in controlling Listeria and E. coli O157:H7, and the poultry industry has reduced the prevalence of Salmonella by at least 50%. As a result of the large produce outbreaks in 2006 and 2007, the produce industry has implemented many changes that are reducing contamination of leafy greens and other produce. Are we where we want and need to be? Not yet, but progress is being made. If the food industry is really reducing the level of contamination, why does it seem that there are so many large scale outbreaks? I believe that the development of PulseNet by Dr. Bala Swaminathan and his colleagues at the Centers for Disease Control (CDC) in 1998 and the introduction of this technology and network to the individual local and state departments’ of health have, for the first time, given us the ability to identify outbreaks that in earlier years would have gone undetected. The CDC Web site defines PulseNet as a national network of public health and food regulatory agency laboratories coordinated by the CDC. The network consists of: state health departments, local health departments and federal agencies (CDC, USDA/ FSIS, FDA). A By STAN BAILEy PRESIDENT “In an ideal world we would never have any foodborne illnesses or outbreaks, but in the world we live in today, we will likely continue to see outbreaks” PulseNet participants perform standardized molecular subtyping (or “fingerprinting”) of foodborne diseasecausing 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 avail- able on-demand to participants, thus, allowing for rapid comparison of the patterns. The objectives of PulseNet are to detect foodborne disease clusters by PFGE, allow for real-time communication among state, local health departments, and international partners, facilitate early identification of common source outbreaks, and help food regulatory agencies identify areas where implementation of new measures are likely to increase the safety of our food supply. Specifically, PulseNet assists epidemiologists in investigating outbreaks by helping to separate outbreak-associated cases from other sporadic cases. In addition to the numerous benefits, the CDC lists a number of limitations for the PFGE method including that the method is time consuming, requires a high degree of skill, does not work for everything, bands are bands not sequences, and some strains are untypable by PFGE and caution that “relatedness” should be used as a guide, not true phylogenic measure. One limitation of the PulseNet is the lack of epidemiological resources at the local, state and federal level. Despite these limitations, most foodborne outbreaks in recent years have been initially identified through the PulseNet. Without PusleNet it is probable that many smaller outbreaks would never be identified. Does finding more outbreaks mean our food supply is less safe? I would argue the opposite. With a better ability to identify outbreaks, we have a better opportunity to prevent individual cases of foodborne disease. Data from the CDC shows that in the time since PulseNet was introduced there are approximately 30 to 50% less cases of food poisoning caused by E. coli O157:H7, Listeria, and Campylobacter and 10 to 20% fewer cases from Salmonella than in the years 144 FOOD PROTECTION TRENDS | MARCH 2009

Food Protection Trends - March 2009

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