Listeria monocytogenes Biofilms in the Food Industry: Is the Current Hygiene Program Sufficient to Combat the Persistence of the Pathogen?

Abstract

Biofilms contain microbial cells which are protected by a self-produced matrix and they firmly attach themselves to many different food industry surfaces. Due to this protection, microorganisms within biofilms are much more difficult to eradicate and therefore to control than suspended cells. A bacterium that tends to produce these structures and persist in food processing plants is Listeria monocytogenes. To this effect, many attempts have been made to develop control strategies to be applied in the food industry, although there seems to be no clear direction on how to manage the risk the bacteria poses. There is no standardized protocol that is applied equally to all food sectors, so the strategies for the control of this pathogen depend on the type of surface, the nature of the product, the conditions of the food industry environment, and indeed the budget. The food industry performs different preventive and corrective measures on possible L. monocytogenes-contaminated surfaces. However, a critical evaluation of the sanitization methods applied must be performed to discern whether the treatment can be effective in the long-term. This review will focus on currently used strategies to eliminate biofilms and control their formation in processing facilities in different food sectors (i.e., dairy, meat, fish, chilled vegetables, and ready-to-eat products). The technologies employed for their control will be exemplified and discussed with the objective of understanding how L. monocytogenes can be improved through food safety management systems.

Effect of Gaseous Ozone on Listeria monocytogenes Planktonic Cells and Biofilm: An In Vitro Study

“…This pathogen can survive and grow in a wide range of foods, such as dairy, meat, seafood and vegetable products, with a high incidence especially in ready-to-eat (RTE) foods [ 6 , 7 ]. The processing environment is considered the most likely source of foodstuffs contamination by L. monocytogenes as the pathogen, when organized in biofilm, can persist for months or even years on surfaces representing a source of recurrent contaminations [ 8 , 9 , 10 , 11 , 12 , 13 ].…”

Bacterial Biofilms and Their Implications in Pathogenesis and Food Safety

“…Although the function of LAP in the pathogenesis of L. monocytogenes has been well documented [48,50], results from recombinant Lactobacillus casei highlights the role of LAP in biofilm formation as well. L. monocytogenes form biofilms on food surfaces or food-touching surfaces [9,16]. Therefore, a significant amount of L. monocytogenes infection might be caused by those in biofilms.…”

Management of Listeria monocytogenes on Surfaces via Relative Air Humidity: Key Role of Cell Envelope

“…Serotypes 4b and 1/2a are mainly found in milk and dairy products [ 11 , 12 , 13 , 14 ]. Different strategies are implemented to fight L. monocytogenes because it can persist via surface adhesion (e.g., polypropylene, stainless steel and biofilm) and by forming with other bacteria [ 6 , 15 , 16 , 17 ].…”

“…Within the food industry, L. monocytogenes is exposed to different environmental conditions (e.g., temperature, relative air humidity [RH]) and, thus, encounters different stresses because contamination can occur at any point in the production cycle, including via handlers or by cross-contamination of raw materials in processing plants [ 15 ]. Some bacteria can adapt to and persist in stressful conditions.…”

“…To fight both persistence and introduction into food processing environments, highly recommended technical strategies include compartmentalization of the processing lines to avoid cross-contamination [ 18 , 19 ]. Cleaning and disinfection programs are performed with chemical agents (e.g., acidic, alkaline or enzymatic agents) and thermal methodologies [ 15 , 20 ]. While complementary alternative strategies, such as bacteriophage, quorum sensing inhibitors and essential oils, have been proposed, RH has been inadequately considered.…”