Background And Historical Significance

For decades, foodborne transmission of pathogenic microorganisms has been a recognized hazard. The predominant foodborne pathogens that were known thirty years ago—Salmonella, Clostridium botulinum, Clostridium perfringens, and Staphylococcus aureus, have been joined by a widening array of pathogens of bacterial, viral, and parasitic origin. Those pathogens that were only seen associated with animals have presented as illness-causing agents in humans.

Traditionally, most foods were either purchased and prepared on the same day or they were removed from the cellar or cupboard as home-canned products. Also, most foods were eaten on the same day they were prepared, thrown away if there were left-overs, or fed to the farm animals. Grocery stores used to carry only locally grown produce, because that was all that was available. However, now the food supply is truly global in nature, in that at almost anytime of the year you can find an abundance of different produce items available in your supermarket as well as a variety of ethnic foods. Also, consumers used to only buy meat from the local butcher or slaughter their own farm animals. Now the meat you purchase in your local supermarket could come from thousands of miles away.


Recent estimates by the Centers for Disease Control and Prevention (CDC) have placed the incidence of foodborne illness at 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths each year in the United States (Mead et al., 1999). These numbers present a much larger incidence of foodborne illness than previously thought. Campylobacter spp. and Salmonella spp. are the predominate causes of bacterial-related foodborne illness. Giardia lamblia is the most often reported foodborne parasite. However, the vast majority of foodborne illnesses are attributed to viruses. The foodborne pathogens with the highest estimated number of deaths are Salmonella spp. Listeria monocytogenes, Toxoplasma gondii, and norwalk-like viruses.

Foodborne Outbreaks

The regulation of the U.S. food supply is primarily divided among two federal agencies—the U.S. Department of Agriculture/Food Safety and Inspection Service (USDA/FSIS) and the U.S. Department of Health and Humans Services/Food and Drug Administration (USHHS/FDA). The FSIS regulates meat and poultry, as listed in the Meat Inspection Act and the Poultry Inspection Act, and egg products as listed in the Egg Products Inspection Act. The FDA regulates all other food commodities as well as exotic animals as listed in the Food Drug and Cosmetic Act.

Food Safety and Inspection Service (FSIS)-regulated commodities

Listeria monocytogenes in hot dogs and possibly deli meats—1998/99 From August 1998 through early February 1999, a total of 100 illnesses caused by L. monocytogenes serotype 4b were reported in 22 states. A total of 21 deaths—15 adults and 6 miscarriages/stillbirths—were associated with this outbreak. The manufacturer voluntarily recalled certain production lots of hot dogs and deli meats that might have been contaminated. The outbreak strain of L. monocytogenes was isolated from an opened and unopened package of hot dogs (CDC, 1998b). It was postulated that the contamination came from dust due to facility construction.

Listeria monocytogenes in deli turkey meat After May of 2000, 29 illnesses attributed to L. monocytogenes were identified in 10 states. Subtyping of the patient isolates found them to be indistinguishable by pulsed-field gel electrophoresis (PFGE). A case-control study identified deli turkey meat as the probable source of infection. The implicated manufacturer recalled implicated product in December 2000 (CDC, 2000b).

Escherichia coli 0157:H7 in fermented sausage Commercially distributed dry-cured salami was associated with an outbreak attributed to E. coli 0157:H7 in California and Washington in 1994 (CDC, 1995). This is the first outbreak associated with dry-cured salami as a source of E. coli 0157:H7. A total of 23 laboratory-confirmed cases were reported. All salami associated with illness was purchased from a local grocery chain deli counter. Research conducted with inoculated salami batter determined the E. coli 0157:H7 could survive the fermentation, drying, and storage process.

Escherichia coli 0157:H7 infections associated with frozen ground beef In

1997, the Colorado Department of Public Health and Environment identified an outbreak of E. coli 0157:H7 infections associated with the consumption of a nationally distributed commercial brand of frozen ground beef patties and burgers. E. coli 0157:H7 isolates from patients and the implicated lot of product were indistinguishable by PFGE. A total of 25,000,000 pounds of ground beef were recalled by Hudson Foods (CDC, 1997).

Food and Drug Administration (FDA)-reguiated commodities

Salmonella Muenchen in unpasteurized orange juice In 1999, an outbreak of salmonellosis was attributed to a commercially produced unpasteurized orange juice (CDC, 1999). A total of 423 confirmed cases and one death were reported in 21 states and three Canadian provinces. The death occurred with an elderly male who resided in an assisted-living facility. The unpasteurized orange juice was manufactured in Arizona and distributed to multiple states and Canadian provinces under several brand names. Analysis of juice from an unopened container, as well as a blender and some juice-dispensing equipment from selected retail stores, yielded S. Muenchen. A comparison of S. Muenchen isolates from the juice, retail equipment, and patients yielded an indistinguishable PFGE pattern. The outbreak investigation was unable to determine the source of the Salmonella contamination. The contamination could have occurred in incoming juice components or within the processing establishment.

E. coli 0157:H7 in apple juice In the fall of 1996, a cluster of E. coli 0157:H7 infections was epidemiologically linked to the consumption of brand A unpasteurized apple juice. Upon completion of the investigation, a total of 70 people with E. coli 0157:H7 infections were identified. Of these 70 persons, 25 were hospitalized, 14 developed hemolytic uremic syndrome, and 1 died. E. coli 0157:H7 was isolated from an unopened container of brand A unpasteurized apple juice. Further investigation at the manufacturing facility did not determine a source for the contamination; however, it was postulated that contamination entered the manufacturing facility on incoming apples since no other juices were associated with illness (Cody et al., 1999).

Salmonella Agona in toasted oat cereal In 1998, an outbreak of salmonellosis was associated with a commercially prepared nationally distributed cereal (CDC, 1998a). This was the first reported Salmonella outbreak attributed with ready-to-eat cereal. A total of 409 confirmed cases and one death occurred in 23 states. Salmonella Agona was isolated from unopened boxes of cereal. Sample analysis of consumer and unopened boxes of cereal yielded an average apparent infective dose between 1 and 45 cells per 30 g serving size (Rosas-Marty and Tatini, 1999). An investigation of the manufacturing facility determined that the contamination may have been attributed to the spraying of a vitamin mix onto the dried cereal.

Escherichia coli 0157:H7 in deer jerky In 1995, an outbreak of E. coli 0157:H7 infection was attributed to jerky made from deer meat (Keene et al., 1997). A total of 6 confirmed and 5 presumptive cases were identified. A deer was shot on one day, eviscerated in the field, dragged to the hunters' vehicle, and hung outdoors for 5 days at ambient temperatures. After skinning, the carcass was dismembered and trimmed by hand. A portion of the meat was cut into strips and marinated in the refrigerator. Following marinating, the meat was dried in a home food dehydrator for 12 to 14 hours between 51.7 °C to 57.2 CC.

Environmental samples of the equipment used to dismember the deer and remnants of the deer skin yielded E. coli 0157:H7. All outbreak associated E. coli 0157:H7 isolates from the jerky, uncooked venison, equipment, deer skin, and human patient isolates were indistinguishable by Pulsed Field Gel Electrophoresis (PFGE). Recovery experiments found that E. coli 0157:H7 could be recovered from experimentally inoculated and dehydrated venison meat.

Salmonella Enteritidis in shell eggs During the last 15 years, there has been a dramatic rise in the incidence of 5". Enteritidis (SE) infections in humans worldwide. In the United States, SE emerged as an important cause of human illness in the 1980's and 1990's. Data from the CDC shows that from 1985-

TABLE 8.1. Salmonella Enteritidis (SE) Outbreaks (1996-1998)
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