Peanut Butter Recalled Due to Salmonella Outbreak

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Nearly 300 people in 39 states have fallen ill since August 2006, linked to a Salmonella outbreak from peanut butter. It is believed to be the first Salmonella outbreak in U.S. history associated with peanut butter. Just two or fewer cases have been reported each day since August, Centers for Disease Control and Prevention (CDC) officials said, and it was only in the past few days that investigators were able to focus in on the particular food responsible. The highest number of Salmonella cases reported were in New York, Pennsylvania, Virginia, Tennessee and Missouri. According to the CDC, about 20% of the 288 infected people were hospitalized but no one has died.

ConAgra Foods is recalling certain jars of Peter Pan and Great Value peanut butter, the house brand sold at Wal-Mart, after it was linked on Wednesday to the nationwide Salmonella outbreak. Both products are manufactured by ConAgra Foods at a single plant in Sylvester, Georgia. The only jars affected have a product code beginning with the number “2111” on the lid, denoting the plant where it was made [1].

In 1996, the first and only known outbreak of Salmonella associated with peanut butter was reported in Australia and blamed on unsanitary plant conditions. During the process of making peanut butter, the nuts are heated to temperatures above 165 °F (74 °C), sufficient to kill Salmonella. However, after the heating step there are a number of opportunities for contamination. A 2000 study to determine the survival characteristics of Salmonella in peanut butter showed that, depending upon formulation, post-process contamination may result in bacterial survival in the product for the duration of the shelf life at 41 °F (5 °C) and possibly 70 °F (21 °C) [2].

Salmonella and E. coli are closely related to each other; homologous (meaning similarity between structures due to their shared ancestry) regions are generally about 85% identical at the nucleotide level [3]. Salmonella enterica are gram-negative (meaning bacteria that that do not retain crystal violet dye in the Gram staining protocol due to an outer membrane, which can exclude certain drugs and antibiotics from penetrating the cell), rod-shaped bacteria that cause diseases of the intestines. Although most Salmonella infections are traced back to dairy, poultry and meat products, Salmonella can grow on just about any food. Chickens and eggs are particular high risk foods.

Salmonellosis is the term for a Salmonella infection. Symptoms of salmonellosis can include diarrhea, fever, dehydration, abdominal pain and vomiting, typically within 8 to 72 hours after the contaminated food was eaten. Additional symptoms may include chills, headache and nausea. Antibiotics are not usually necessary unless the infection has spread from the intestines. Unfortunately, some Salmonella have become resistant to antibiotics, largely due the use of antibiotics to promote the growth of feed animals. Symptoms of salmonellosis usually disappear within 4 to 7 days, and many people recover without medical treatment. However, Salmonella infection can be life-threatening for infants and young children, pregnant women and older adults as well as people with weakened immune systems. The reported incidence of Salmonella illnesses is just over 14.5 cases per 100,000 people [4]. Approximately 40,000 people in the U.S. get sick from Salmonella infection each year, killing about 600 people annually.

The best way to avoid Salmonella infection is to ensure food is thoroughly cooked. Additional precautions suggested by the USDA and CDC include:

• Wash your hands before and after handling food and after using the bathroom, changing diapers, and handling pets.
• Wash your hands, countertops, cutting boards, dishes and utensils with hot soapy water after preparing each food item and before you go on to the next.
• Separate raw meat, poultry and seafood from other foods in your refrigerator. Wash cutting boards, dishes, countertops and utensils with hot soapy water after they come in contact with raw meat, poultry and seafood.
• Cook food to proper temperatures. Don’t eat raw or undercooked eggs, poultry or meat. Reheat other leftovers thoroughly to at least 165 °F.
• Refrigerate food promptly (within 2 hours, 1 hour if temperatures are above 90 °F). Thaw food in the refrigerator, in cold water, or in the microwave – foods should not be thawed at room temperature.

References

1. FDA News, FDA Warns Consumers Not to Eat Certain Jars of Peter Pan Peanut Butter and Great Value Peanut Butter. Feb 2007.
2. Burnett et al. Survival of Salmonella in peanut butter and peanut butter spread. J Appl Microbiol. 2000 Sep;89(3):472-7.
   View abstract
3. Sharp PM. Determinants of DNA sequence divergence between Escherichia coli and Salmonella typhimurium: codon usage, map position, and concerted evolution. J Mol Evol. 1991 Jul;33(1):23-33.
   View abstract
4. CDC. Summary of Notifiable Diseases, United States, 2004. MMWR, 2006; 53:1-84.