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Such errors are extremely rare in commercially canned foods, and most cases of botulism are due to processing errors in home-canned foods. As an added safety measure, home-canned foods should be boiled for 10 to 15 minutes immediately before consumption. The toxin is heat-labile (sensitive), and so the heat treatment will destroy any toxin that may have been produced. Cans that are damaged should be discarded, because they might have small holes through which C. botu-linum could enter. Likewise, bulging cans indicate gas production, which could indicate microbial growth, and should be discarded. ■ botulism, p. 672 ■ neurotoxin, p. 472

the initial contamination by bacteria such as E. coli O157:H7 normally occurs on the surface and is easily destroyed by searing the exterior of whole meats such as steaks, grinding the meat distributes those same bacteria throughout the food.

Foodborne Infection

Unlike foodborne intoxication, foodborne infection requires the consumption of living organisms. The symptoms of the illness, which usually do not appear for at least 1 day after ingestion of the contaminated food, usually include diarrhea, but vary according to the type of organism ingested. Thorough cooking of food immediately before consumption will kill the organisms, thereby preventing foodborne infection. Escherichia coli O157:H7 and Salmonella and Campylobacter species are examples of organisms that cause foodborne infection (figure 32.8).

Salmonella and Campylobacter

Salmonella and Campylobacter are two genera commonly associated with poultry products such as chicken, turkey, and eggs. Inadequate cooking of these products can result in foodborne infection. Cross-contamination of other foods can result in the transfer of pathogens to those foods. For example, if a cutting board on which raw chicken was cut is then immediately used to cut up vegetables for a salad, the salad can become contaminated with Salmonella or Campylobacter species. ■ Salmonella, p. 616 ■ Campylobacter, p. 617

Escherichia coli O157:H7

Escherichia coli O157:H7 causes bloody diarrhea that sometimes develops into hemolytic uremic syndrome (HUS), which is life-threatening. In the past decade, E. coli O157:H7 has caused several large food poisoning outbreaks, including an epidemic in Japan in 1996 that sickened more than 9,000 people and a 1993 outbreak in the United States that spread over four states. The latter epidemic was traced to undercooked contaminated hamburger patties served at a fast-food restaurant. Ground meats are a troublesome source of foodborne infection. While

• Most bacteria that normally compete with Staphylococcus aureus are either killed by cooking or inhibited by high salt conditions.

• Food handler inoculates s. aureus onto food.

• s. aureus grows and produces toxin when food is allowed to slowly cool or is stored at room temperature.

• A person ingests the toxin-containing food. Symptoms of staph food poisoning, including nausea, abdominal cramping and vomiting, begin after 4-6 hours.

Figure 32.7 Typical Events Leading to Foodborne Intoxications

• Clostridium botulinum endospores, common in soil and marine sediments, contaminate many different foods.

• Endospores survive inadequate canning processes. Canned foods are anaerobic.

• Surviving C. botulinum endospores germinate, grow, and produce toxin in low-acid canned foods.

• A person ingests the toxin-containing food. Symptoms of botulism, including weakness, double vision, and progressive inability to speak, swallow, and breathe, begin in 12-36 hours.

Staphylococcus aureus and Clostridium botulinum

Figure 32.7 Typical Events Leading to Foodborne Intoxications

• Incomplete cooking fails to kill all pathogens. Surviving Salmonella and/or Campylobacter can multiply as food is cooled slowly or stored at room temperature.

• Live organisms are ingested. They multiply in the intestinal tract and cause disease. Symptoms include diarrhea, abdominal pain, and nausea.

Figure 32.8 Typical Events Leading to Salmonella, Foodborne Infections

• Incomplete cooking fails to kill all pathogens. Even low numbers of surviving E. coli O157:H7 can cause illness.

• Live organisms are ingested. They multiply in the intestinal tract and cause disease. Symptoms include severe abdominal pain and bloody diarrhea.

Campylobacter, and E. coli 0157:H7

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