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From: Food Quality & Safety magazine, February/March 2007

The Reputation Drain

Listeria Lurks in Store Drains and can Damage Store Image if not Controlled Properly

by Dale Grinstead, Phd

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.

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.

Traditional drain cleaning practices can facilitate the spread of Listeria through the creation of potentially harmful airborne droplets. Traditional cleaning practices involve scrubbing drains with brushes or pads, which can spray droplets from inside the drain into the store environment. These aerosols, which may contain Listeria, can deposit themselves on food-contact surfaces and eventually on food.

Traditional drain cleaning practices also have the added drawback of being labor intensive: They require extensive training and all are generally unpleasant jobs. This can lead to retail staff or cleaners overlooking the task. Putting off or avoiding the cleaning of drains in a food retail setting only increases the chances of dirt buildup and creates an ideal breeding ground for Listeria.

Listeria-Controlling Strategies

Because Listeria causes serious illness and grows in difficult-to-clean and hidden areas, controlling the organism can be a daunting task. By using a drain-cleaning program and incorporating new cleaning technology, however, there are easier ways to control this organism in retail establishments.

Identification: The first step in eliminating and controlling Listeria is to identify it. Keep swab testing kits on hand to regularly check drains, countertops and other surfaces for Listeria. Retailers should take individual swabs of floor and sink drains as well as countertops. The send test swabs to an independent laboratory for analysis. Usually labs will send back a confidential report detailing the results within a few weeks.

Elimination: Regardless of whether or not Listeria is found, the organic soil and bacteria need to be eliminated from drains to control the organism. This is a two-step process that involves cleaning, followed by sanitizing or disinfecting. Listeria will not be eliminated if the drains are not first thoroughly cleaned because sanitizers do not remove organic soils, and soil interferes with the antimicrobial action of sanitizers and disinfectants.

New cleaning products such as foaming drain cleaners are the best, most effective type of drain cleaners because they cling to vertical surfaces and can separate soil and bacteria from the sides of the drain. These soils can then be flushed down the drain without leaving behind remaining traces.

When using a foaming cleaner, connect the product to a water source and spray into drains, where the cleaner latched onto soil particles and breaks them up. This eliminates the need to disassemble the drain, which helps prevent Listeria droplets from being released into the air through scrubbing and greatly simplifies the cleaning process. After about a minute, the drain is flushed thoroughly with water. Use a sanitizer or disinfectant once the drain is clean.

Additional brushes and pads are not required. Using a foaming cleanser with a sprayer is a no-touch cleaning process, which can greatly reduce the risk of direct employee contact with the chemical concentrate and the organic material. Any cleaner used should not be harmful to the soft metals used to make drains, such as brass, cast iron or aluminum.

Control: After the drain has been cleaned and sanitized, the final step in keeping Listeria out of store drains is to maintain the cleanliness of the area by following proper food preparation practices and diligent cleaning on a regular basis. Cleaning staff, as well as other store personnel, must be properly trained on how to clean drains as well as food-contact surfaces. Wall charts and easy-to-read instructions with icons and images can help personnel easily understand cleaning and hygiene practices.

Finally, store managers can design auditing surveys to track the cleaning practices required to make sure each area of concern is properly attended on a regular basis.

Protect Food, People and Reputation

Incorporating new developments in cleaning technology that improve the safety and cleanliness of stores will help food retailers reduce the risk of spreading Listeria and other food-borne pathogens. These developments make it easy to train new workers quickly on the proper procedures because products are easier and safer to use. A cleaner, safer store can provide a better customer experience while enhancing the store’s reputation and protecting its brand.

Dale Grinstead, PhD, a senior research scientist for JohnsonDiversey Inc. (Sturtevant, Wis.), has more than 12 years of industrial R&D experience. Reach him at 262-631-4433 or



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