Listeria outbreak

A deadly three month listeria outbreak has been causing consumers to avoid purchasing cantaloupes as the outbreak claims the lives of 28. Another 133 people have been hospitalized with the deadly disease. The outbreak has affected 26 states in total.

A map of the listeria outbreak. Photo from Creative Commons.

In a report released earlier this month, the FDA addressed their findings in their three-month-long research into the cause of the listeria outbreaks. The study found that the listeria was not present in the fields where the cantaloupes were grown. Instead the bacterial infection was found to be present in the cold storage facilities of the single large farm where the tainted melons came from. These storage facilities are where cantaloupes are stored before going to market.

According to the report, the conditions at the Colorado-based Jensen Farms allowed the outbreak to occur. These conditions were a perfect storm for the spread of listeria. The conditions which led to the outbreak were a floor that allowed water to gather and pool. The floor and machinery in the packing area were not easily cleanable and could not be thoroughly sanitized, and equipment for processing and packaging the cantaloupes had previously been used for other agricultural products. The report also cited there was no pre-cooling system to get field heat out of the fruit before processing and storing.

The issues cited in the report are important because of how listeria works. Unlike other bacteria, listeria has a unique trick that allows it to grow in the cold and continue to spread. This evolutionary quirk, along with the porous nature of the cantaloupe, allowed the listeria to survive and thrive in the cold storage facilities. The pooling water provided an optimal breeding ground for the bacteria and given the chance it would jump to and thrive in the fruit.

Another issue stated in the report is the problem of condensation forming inside of warm cantaloupe that is slowly cooled in the storage unit. This provided yet another cold wet environment for listeria to grow in. This was the first case of listeria-tainted melons in the US. The backtracking of the infection proved a unique challenge for the FDA.

While the report explains how the listeria was spreading through cantaloupes and infecting the general public, the public may never know how the bacteria got into the storage facility in the first place. While there is no definite evidence on the source of the bacteria, the FDA report does provide a possible source for the bacteria. All cantaloupe produced by the farm couldn’t be sold on market and much of it was sold to a nearby cattle farm. The intestines of cattle is one of many places that are known to contain listeria.

While this may have been the first outbreak on US soil, it may not be the last. Consumers must wonder how their food is prepared before they buy it in the stores or on the market. It’s vital that consumers become more aware and encourage producers to use safer food processing methods.