It is difficult to ignore the news headlines announcing risks and tragedies associated with the various microorganisms and illnesses threatening the food industry, including E.coli, Salmonella, Avian Flu and so on. In the past 20 years, one serious pathogen – Listeria monocytogenes – has been a major concern to the food industry. Of all the known foodborne pathogens, it has one of the highest mortality rates.
Explore this issueFebruary/March 2007
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In the United States, Listeria monocytogenes, or Listeria, causes about 2,500 illnesses a year, yet it results in more than 500 deaths – a 20 percent mortality rate. Compare that with Salmonella, which causes about 2 million illnesses a year but results in about the same number of deaths as Listeria, according to the Centers for Disease Control and Prevention (Atlanta, Ga.)Although cases of Listeriosis, the serious illness caused by Listeria, are not reported as regularly as other foodborne illnesses, when someone does get ill from Listeria they have a high chance of dying from the illness.
An outbreak of Listeria can not only cost a food retail store millions of dollars, it can also cause severe damage to its reputation. In response to these frightening statistics, experts have conducted considerable research on Listeria. Based on their findings, new technology have been developed to help the food industry better identify, eliminate and control Listeria.
Get To Know Listeria
Listeria monocytogenes is the most well-known Listeria species and the greatest concern for food safety because of its ability to withstand harsh conditions.
This organism is capable of forming and growing in biofilms. Bacteria in biofilms are more difficult to kill with sanitizers and disinfectants because of the protective film or slime layer associated with the biofilm. This characteristic can make Listeria monocytogenes difficult to control in the environment – particularly in areas frequently wet (and where the organism thrives), such as floor drains, mats and cutting boards.
One of the most important characteristics of Listeria that makes it a food-safety concern involves its capacity to grow at refrigeration temperatures. While refrigeration is used to control the growth of most other food-borne pathogens, Listeria is capable of growth at 5 ° C.
Finally, food products, or items that contain Listeria cells do not look, smell or taste different.
Where Listeria Thrives
In addition to its ability to grow at refrigeration temperatures, Listeria is a ubiquitous bacterium, which means it can be found nearly anywhere, this makes it difficult to keep it out of a food retail environment. Difficult-to-clean and frequently missed nooks and crannies harbor Listeria. One of the most common harborage sites for Listeria: the drain.
Although store drainage systems are an especially critical area to clean regularly and hygienically to prevent the spread of Listeria, they are often not held to the same high standards of cleaning associated with food preparation areas. And though retailers have food- safety programs in place to prevent the outbreak of foodborne illnesses, these cleaning and sanitation programs tend to focus on the obvious food-contact areas, such as food display cases, slicers, walls, grinders, sinks, floors and countertops. This is due in part to the perception that because food items or products do not come into direct contact with drains (unlike preparation surfaces or utensils) they will not be able to contaminate food.
The truth remains that Listeria present in drains can easily reach food and food-contact areas. Listeria pathogens in floor drains may be carried on shoes and transferred onto food preparation areas or directly onto food items themselves when someone picks up a dropped object from the floor. Additionally, pests like fruit flies, drain flies or cockroaches have the potential to spread Listeria pathogens from drains to other areas of the facility.