Feb 15, 2007 (CIDRAP News) – The US Food and Drug Administration (FDA) warned consumers yesterday to avoid certain peanut butter brands linked to a slow but sustained Salmonella outbreak that has sickened 288 people in 39 states since August.
The peanut butter implicated in the outbreak is contaminated with Salmonella enterica serovar Tennessee and comes from a ConAgra plant in Sylvester, Ga., that produces Peter Pan and Great Value brand products with a product code on the lid that begins with the number 2111, the FDA said in a press release.
Consumers who have any jars of the two brands with the 2111 code purchased after May 2006 should discard the product, the FDA said. ConAgra has voluntarily recalled the affected products and has stopped production until the contamination cause can be identified and eliminated.
"Although none of our extensive product tests have indicated the presence of Salmonella, we are taking this precautionary measure because consumer health and safety is our top priority," said Chris Kircher, spokesman for ConAgra foods, in a press release yesterday.
The outbreak appears to be ongoing, the FDA said.
The Centers for Disease Control and Prevention (CDC), in an alert sent to public health workers today, said illness onset dates are known for 140 patients and range from Aug 1, 2006 to Jan 21. Up to two new cases were reported nationwide each day in January, the CDC said.
Two closely related DNA fingerprints of S Tennessee have been associated with the outbreak, the CDC said. The DNA patterns were identified through PulseNet, a national network of public health laboratories. S enterica typically causes fever and nonbloody diarrhea that resolves in a week.
The CDC said that of 120 patients for whom clinical information is available, 31 (26%) were hospitalized. No deaths have been reported. Five Minnesota patients, one of whom was hospitalized, have been connected to the outbreak, said Buddy Ferguson, a Minnesota Department of Health spokesman. Illness onsets are known for four patients and ranged from September to January, he told CIDRAP News.
Extensive epidemiologic studies allowed the CDC to identify Peter Pan peanut butter with the 2111 product code as the likely cause of illness, but Great Value peanut butter with the same product code is produced at the same plant and is believed to be at risk for contamination, the FDA said.
The FDA said its investigators are at the ConAgra plant reviewing records, collecting product samples, and conducting tests for S Tennessee.
The current outbreak is the second known instance of Salmonella contamination in peanut butter. In 1996, 15 people were sickened after eating peanut butter that was contaminated with S enterica serovar Mbandaka, according to a 1998 report published in the Australia and New Zealand Journal of Public Health. Investigators traced the contamination source to roasted peanuts.
Pasteurization, shelf-life issues raised
Health officials and peanut butter industry representatives are examining peanut butter production methods and how the products involved in the recall might have become contaminated, the CDC said.
Israeli researchers recently tested the heat tolerance of three Salmonella strains in peanut butter and found that current peanut butter pasteurization processes, with temperatures from 158 to 167ºF (70 to 75ºC) applied for up to 20 minutes, don't consistently destroy the organism. They found that some Salmonella survived, even when the peanut butter was heated to 194ºF (90ºC) or for longer periods, up to 50 minutes. Their results appeared in the November 2006 issue of the Journal of Food Protection.
They noted that Salmonella organisms might have increased heat resistance in foods that have low water and high lipid content, such as peanut butter or chocolate.
The findings raise important food safety concerns, the authors wrote, particularly when outbreaks indicate that only a few cells may be enough to cause disease when consumed in foods that have little water.
Such foods are common snacks for young children, the authors pointed out. "Increased consumption of these food types could result in more frequent outbreaks of salmonellosis unless appropriate management steps are taken," they wrote.
Heating peanut butter for longer periods or to higher temperatures could denature or brown the peanut butter, the researchers said. They concluded that food processors should investigate other Salmonella inactivation methods to make their products safer.
Meanwhile, researchers at the University of Georgia have found that Salmonella can survive in peanut butters and spreads, depending on their formulation, throughout their 24-week shelf life when stored at 41ºF (5ºC). They tested five peanut butters and two spreads. All tested positive for Salmonella when stored at 41ºF; when stored at 69.8ºF (21ºC) for the shelf life, all but one spread tested negative for the pathogen.
Feb 14 FDA press release
CIDRAP overview of salmonellosis
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Shachar D, Yaron S. Heat tolerance of Salmonella enterica serovars agona, enteritidiis, and typhimurimum in peanut butter. J Food Protec 2006 Nov;69(11):2687-91 [Abstract]
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