Listeria is a very common bacterium that adapts well in many environments. Once established in a food production facility, some strains of Listeria can be very difficult to eliminate. This post highlights the most common hideouts for Listeria in food production environments, and offers useful advice on how to optimise environmental Listeria control.
Listeria – an overview
Listeria bacteria are very common in the environment and can be found in soil, water, sewage, animal guts and feces, and on raw foods.
There are several species of Listeria, but only Listeria monocytogenes is associated with the human foodborne infection listeriosis. People usually contract listeriosis from eating contaminated ready-to-eat foods such as salads, raw fruit and vegetables, sandwiches, deli meats, smoked fish, cooked shellfish, sushi, raw milk, unpasteurised cheese and ice cream.
Although infections are very rare, listeriosis is one of the most serious foodborne illnesses humans can contract. Pregnant women, newborns, older adults and people with impaired health are especially vulnerable to infections. Symptoms range from mild flu-like illness to severe blood poisoning and meningitis.
Every year about 2,200 people in Europe and 1,600 people in the United States contract listeriosis. Most people are hospitalised, while one in five (20 percent) of those infected will die.
Consequently, control of Listeria in ready-to-eat foods and in foods intended for consumption by infants and people with impaired health is strictly required by law, both in Europe and the USA.
When to be concerned about Listeria?
Because Listeria is common in the environment and can be found in soil, water, animal guts and on raw foods, the bacteria can easily be introduced into and spread throughout food production facilities.
Listeria also can form biofilms that help them attach to the surface of floor, drains and equipment – making them more difficult to remove during cleaning, and protecting them from drought, heat and standard cleaning and disinfection chemicals. Listeria biofilm is often the source of food product cross-contamination.
Additionally, Listeria can grow in cold environments and can survive freezing temperatures. These conditions are often used to control microbial growth, but for Listeria they serve only to restrict the growth of competitors. This means that refrigerated and frozen foods still are at risk.
Most ready-to-eat food processing environments are chilled and provide the nutrients and moisture required for Listeria growth. So, there’s good reason for being concerned about Listeria contamination if you produce ready-to-eat, chilled food.
Listeria hideouts and control in food production facilities
1. Floors and drains
Floors that are made of inappropriate materials or that have been installed poorly can lead to static water pools, water trap points or water absorption. Badly constructed or poorly sealed wall-to-floor or drain-to-floor joints often lead to water becoming trapped, as can poorly maintained and damaged floors with cracks, holes or gaps. All these situations can lead to Listeria colonisation. Consequently, the appropriate selection, installation and maintenance of your production floor are very important with regard to Listeria control.