While US shops and consumers hunt down and throw out potentially contaminated jars of Peter Pan Peanut Butter, health officials continue to investigate exactly how some of them became contaminated with Salmonella.

The Food and Drug Administration (FDA) warned US consumers earlier this week not to eat jars of Peter Pan Peanut Butter and Great Value Peanut Butter with product codes starting “2111” because they could be contaminated with Salmonella.

The product code is stamped on the lids of the jars.

The salmonella strain the peanut butter jars could be contaminated with is a particular strain of the food-borne bacteria known as Salmonella Tennessee.

The peanut butter with product code 2111 is made in Sylvester, Georgia by food producer ConAgra Foods Inc. Other jars of peanut butter sold by Great Value that do not carry the 2111 product prefix are not affected since they are made by other companies.

If you have Peter Pan or Great Value peanut butter with a product code starting with 2111 on the lid of the jar you should throw it away, said the FDA. The jars will have been on sale since May 2006.

The warning was issued following an investigation by the Centers for Disease Control and Prevention (CDC) and other health officials into 288 reported cases of food related infections in 39 states that were traced to eating Peter Pan peanut butter.

According to the CDC, most of the people affected were residents of New York, Pennsylvania, Virginia, Tennessee and Missouri. No deaths were reported although 20 per cent of those affected had to be admitted to hospital for treatment.

The first consumer to be affected was probably back in August last year. Peter Pan peanut butter was identified as the likely source of the infection, and because Great Value peanut butter is made in the same plant, jars of that brand from that plant have also been recalled.

Exactly how the bacteria got into the jars of peanut butter is still a mystery. The process of making peanut butter heats it to a very high temperature to kill all such pathogens. It is possible said some of the health officials, that the bacteria got in through contaiminated jars. Or perhaps it was on equipment that came into contact with the product after it was heated and before it was sealed in the jar.

Symptoms of Salmonella include fever, stomach ache and diarrhea. Salmonella is not normally life-threatening in healthy people. But it can be very serious for anyone with a compromised immune system, such as someone who is elderly and frail, or already ill with a serious infection, or very underweight.

If you think you have eaten contaminated peanut butter from one of these jars and are feeling ill with symptoms like these you should contact your doctor straight away.

Meanwhile ConAgra, the company that owns the Georgia plant where the Salmonella was traced to, has stopped production of peanut butter, has destroyed stored jars at the plant and is recalling all jars of the product with the 2111 code prefix.

FDA officials are at the plant looking through records, collecting samples and conducting tests for Salmonella Tennessee to help locate the source.

Normal operation at the Georgia plant will not resume until the exact source of the contamination in the factory has been found and eliminated.

Every year about 40,000 Americans get sick and 600 die from being infected with foodborne Salmonella of various types.

The species of Salmonella that causes foodborne illnesses has many different serological varieties or serovars, each of which is classified according to the type of reaction that it causes in the body, or more specifically, the type of surface antigens infected cells produce to help the immune system fight the infection.

Salmonella Tennessee belongs to the serogroup C1, it is a rare strain of Salmonella and has some unexpected properties, such as its ability to ferment lactose as well as sucrose.

Nowadays Salmonella serovars are identified using DNA fingerprinting, but in earlier times detection of this strain was often missed because scientists were not expecting to find a Salmonella that could ferment lactose.

The US is the world’s largest peanut butter supplier and consumer. Alabama, Florida and Georgia grow 60 per cent of the peanuts used in peanut butter.

Pure peanut butter has high levels of monounsaturated fats, and the anti-oxidant p-coumaric acid.

Peanuts are an excellent source of protein, vitamins B3 and E, and they also contain magnesium, folate, fibre and arginine, an essential amino acid.

Click here for Questions and Answers relating to this outbreak (CDC, PDF file)

Click here to see Salmonella Taxonomy (University of British Columbia Bioinformatics Centre).

Written by: Catharine Paddock
Writer: Medical News Today