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Modern Diseases for Modern Times

Fast food restaurants one of modern society’s symbiosis, have compound an already serious infectious disease dilemma, that of widespread food borne illness. In 1992, a major outbreak f a deadly illness erupted in four western American states when hundreds of people who had eaten hamburgers at a fast food chain suffered bloody diarrhea, after which many experienced serious kidney damage. At least four people died. The microbe responsible for the outbreak was a pathogenic strain of Escherichia coli, a species found in virtually every mammal’s normal intestinal flora. This strain (called E.coli 015:H7), unknown only a decade before was introduced into ground beef during processing, when feces from slaughtered dairy cows was inadvertently mixed with the meat. Public health investigators discovered that 100,000 pounds of the contaminated meat was ground and formed into patties. The ground beef contained viable bacteria that could infect a person and cause illness unless the meat was thoroughly cooked. Compared to Salmonella and other food borne pathogens, which require ingestion of thousands of bacteria to produce symptoms, the presence of just a few E.coli 0157:H7 organisms can cause overt disease.

It is now estimated that 20.000 cases of E.coli 0157:H7 infection occur every year in the United States and Canadian health authorities claim that the number may be 10 times that high. The deadly E.coli strain has also invaded home kitchens, where improperly cooked ground meats (including pork, poultry, and lamb as well as beef) lead to sporadic outbreaks of disease. Measures that once controlled such outbreaks by minimizing contamination and by setting cooking temperatures to ensure that dangerous microbes were killed are no longer adequate, according to Morris Potter of the Centers for Disease Control. Something has changed and these measures are no longer able to destroy the bacteria. Until the problem can be identified and corrective measure instituted, eating medium rare ground meat will continue to be risky business.
Why have these outbreaks been associated with hamburger, but not steaks and other ungrounded meats? Because microbes contaminate only the surface of meats, steaks, roasts and other ungrounded meats are virtually sterilized by cooking since their surfaces are next to the heat and achieve adequate temperatures. Grinding the meat, however introduces the microbes at the surface into the interior of the meat, essentially turning the entire mass of the meat into surface area. The bacteria in the interior are often protected from being killed by cooking because the center of the meat is cooler than the outside surfaces.
In light of the recent E.coli outbreaks, the Food and Drug Administration (FAD) recommends that  hamburger (indeed all meat) be cooked until the center reaches 86.1oC (155oF) or until the interior is no longer pink and the juices run clear. These recommendations are especially important to follow in light o f new discoveries on the prevalence of the pathogen. E.coli 015:H7 is more common that Shigella (the prototype agent of bacterial dysentery) and frequently lives in the intestine of healthy cattle.

As microorganisms evolve, new strains and species will continue to create new healthy problems. Such changes in populations are inevitable, natural selection favoring the species best adapted for surviving and reproducing in constantly changing environments. As we change, so will the microbe that interacts with us and so must our procedures for controlling them? Perhaps optimism will soon return without over-confidence tagging along.
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