By; James Peacock

On January 10, 2017, the FDA issued a warning letter to Aspen Hills, Inc. about the presence of Listeria monocytogenes bacteria at one of the company’s facilities. The facility in question, located in Iowa, was visited by FDA officials between September 27 and October 6, 2016. Health officials took samples from a wide variety of locations across the facility. They received sample positive for Listeria contamination from several different areas, including on ladders, pallet jacks, various baskets, and other areas that deal with the making and packaging of frozen cookie dough products. There were also several samples taken from the cookie dough itself which tested positive for Listeria monocytogenes bacteria. Because of the presence of Listeria bacteria in both the facility’s environment and the finished products, the FDA has urged Aspen Hills to take more aggressive action against these contaminations. The FDA acknowledged previous responses from Aspen Hills regarding the Listeria contamination, but charge that not enough has been done to resolve the issue. Aspen Hills was given 15 business days to respond to the letter.

This warning letter comes on the heels of a series of recalls from last year that were linked to Aspen Hills. In September 2016, Blue Bell and other ice cream brands were forced to recall a number of products due to the presence of Listeria bacteria. It has now become clear that the source of the contamination was Aspen Hills and not the companies that they supplied raw cookie dough to. An investigation done by the FDA revealed this Aspen Hills contamination, which led to the series of correspondence that culminated in the January 10 warning letter. Aspen Hills had issued a recall on October 10, 2016, after they were linked to the Blue Bell contamination. This recall included products made between February 2 and September 7, 2016. These products were shipped to retailers and supplied to companies in Alabama, Arkansas, Florida, Georgia, Kansas, Kentucky, Louisiana, Mississippi, Missouri, New Mexico, North Carolina, Oklahoma, South Carolina, Virginia, Texas, and Tennessee. Due to the frozen nature of these products, it may still be possible that the contaminated cookie dough could be found in the freezers of consumers. More information about the recall can be found here.

Throughout this investigation, health officials have made use of testing procedures in order to help narrow down the source and cause of this Listeria contamination. In many cases, the process of pulsed-field gel electrophoresis (PFGE) is used. This type of testing reveals is the bacteria’s DNA fingerprint. This fingerprint is unique to the bacteria and strain involved in the investigation. The DNA fingerprint is then uploaded to the PulseNet system. The PulseNet system is a database of DNA fingerprints maintained by the CDC. If a saved sample matches another sample, there may be a connection between the two. Also used heavily in this investigation was the process of whole genome sequencing (WGS). This takes a more detailed look at the genetic makeup of a bacterial sample, allowing health officials to draw more conclusions about the nature and extent of the contamination. Over the course of this investigation, FDA officials used the WGS method to test 15 different samples. All of these samples contained the same strain of Listeria monocytogenes bacteria. These samples also tested as a match to three other samples taken in the past from finished ice cream products that use Aspen Hills frozen cookie dough as an ingredient, linking Aspen Hills to other reported contamination.

Listeria monocytogenes bacteria are an especially dangerous form of foodborne pathogen. They have the ability to survive and even thrive, in very cold environments. This means that freezing the bacteria will not kill them, nor will it hamper their growth. This was seen in the Blue Bell outbreak in 2015, in which 10 people were sickened with Listeria poisoning after consuming frozen ice cream. Because Listeria bacteria has also been linked to numerous raw products, including sprouts and raw milk, the CDC recommends that the only way to properly remove Listeria bacteria is to cook products thoroughly. This makes it especially important to cook meats to an internal temperature of 160 in order to prevent the survival of any contamination.

Listeria monocytogenes bacteria first became known as a foodborne illness in 1981. Although it had received previous study, it was not until a major outbreak in Canada that the pathogen began to gain more attention. The CDC began to track Listeria infection more than 30 years ago. In the 1990s, most outbreaks were caused by deli meats and hot dogs. Since then, though, there have been Listeria outbreaks caused by a wide variety of products, including unpasteurized juices and milk, the products made with these raw liquids, sprouts, and other vegetables, and smoked seafood. Deli meats continue to be a leading cause of Listeria outbreaks. The CDC now estimates that there are about 1600 cases of illness caused each year by Listeria bacteria. This leads to about 260 deaths per year. There are several risk factors that make an individual more likely to develop a Listeria infection. Newborns, older adults, and people with suppressed immune systems are all at an increased risk. Pregnant women are also about 10 times more likely to develop a Listeria infection.

The testing process for a Listeria infection is a simple tissue sample used to foster the growth of a bacterial culture. If Listeria is seen in the developed culture, then the individual who provided the sample has tested positive for a Listeria infection. This infection is usually treated with antibiotics. The Listeria poisoning itself may not produce symptoms for up to two months after the infection, although symptoms usually present within 3-10 days. Listeria infections often produce similar symptoms to other foodborne illnesses, including fever and diarrhea. However, if the infection becomes invasive, meaning it has left the gastrointestinal system, the symptoms can worsen. In pregnant women with invasive Listeria, fever, fatigue, muscle aches, and diarrhea are all common symptoms. However, Listeria has been known to cause miscarriage, stillbirth, infection in newborns, or premature delivery. In individuals with invasive Listeria who are not pregnant, fever, diarrhea, headache, stiff neck, confusion, convulsions, loss of balance, and muscle aches are all common symptoms. If you or a loved one begin to show the symptoms of Listeria poisoning, contact a medical professional.