Biofilms are a persistent, ubiquitous threat to food manufacturing industries worldwide. From dairy, meat, produce, poultry, and ready-to-eat meat and deli products, biofilm is a primary concern at every level of the food production chain, from the farm level and harvesting to food processing environments and manufacturing plants. Biofilms are difficult to remove; They are also often resistant to routine cleaning, sanitization, and disinfection procedures, pose significant health risks, and degrade equipment.
Even when a food processing surface appears to be clean, the presence of biofilms is a potential hazard that must be eliminated and prevented from reoccurring. Before this can be done, it is crucial to understand what biofilms are, how they form, and how they can be controlled.
What are Biofilms?
In brief, biofilms are communities of microorganisms (like bacteria) that stick to surfaces.
As defined by the Centers for Disease Control and Prevention (CDC), “A biofilm is an assemblage of microbial cells that is irreversibly associated (not removed by gentle rinsing) with a surface and enclosed in a matrix of primarily polysaccharide material. Noncellular materials such as mineral crystals, corrosion particles, clay or silt particles, or blood components, depending on the environment in which the biofilm has developed, may also be found in the biofilm matrix. Biofilm-associated organisms also differ from their planktonic (freely suspended) counterparts with respect to the genes that are transcribed.”
Biofilms are complex systems that are sometimes compared to multicellular organisms. They can be composed of a single species or a combination of them. In many cases, biofilms are only bacteria, but they can also include other microorganisms, such as fungi and algae, creating a microbial stew of sorts. Their secret to resilience is their matrix, which is a sort of slimy goo, made up mostly of complex sugars, proteins, and nucleic acids (such as DNA) that many bacteria secrete, allowing them to form slimy bacterial communities. Through this slime, different bacteria can share nutrients and water, divvy up labor, and protect each other. They can also send signaling proteins to let them communicate, and they can even swap DNA to pass along their genes. The matrix also acts as a shield, covering and protecting these microorganisms from heat, cold, ultraviolet light, and most types of chemical disinfectants and biocides designed to destroy bacteria.
To make matters worse, their thick, slimy matrix often makes biofilms antibiotic-resistant. One study found that bacteria in biofilm were 1,000 times more resistant to antibiotics than the same bacteria were when they were on their own. Biofilms can also be invisible on surfaces, making them even harder to control.
Related: Vital Oxide vs. Bacterial Biofilm
Foodborne Diseases Associated With Food Industry Biofilms
Biofilms cause approximately 60% of foodborne illness outbreaks. Foodborne diseases associated with bacterial biofilms on factory equipment or food matrices (a food matrix, as defined by USDA, is "the nutrient and non-nutrient components of foods and their molecular relationships, i.e., chemical bonds to each other.") may arise via infections or intoxications. In either case, the presence of biofilms on food processing equipment poses threats to human health. Toxins, for instance, can be secreted by biofilm found on food processing equipment. From there, they can contaminate a food matrix, causing an individual intoxication or multiple intoxications in the case of an outbreak.
The central locations for biofilm development depend on the food factory type. Still, they may include tables, food-contact surfaces, packing material, liquid pipelines (such as water and milk pipelines), storage silos for raw materials and additives, dispensing tubing, etc.
Common Foodborne Bacterial Pathogens
Biofilm is a natural process that pathogens – including those commonly leading to foodborne illness outbreaks – use to survive. Here are a few examples of common foodborne bacterial pathogens and their capacity to form biofilms on food surfaces.
The ability of Salmonella to form biofilms contributes to its resistance and persistence in food processing environments. For instance, S. Typhimurium colonizes and can form biofilms on various types of produce, while S. enteritidis is often found within and on eggs. Additionally, S. enterica can grow on stainless steel surfaces and is ubiquitous in food processing plants.
Listeria Monocytogenes (Lm)
The Gram-positive bacterium L. monocytogenes is a dangerous foodborne pathogen. According to the Food Safety Inspection Service (FSIS), Listeria monocytogenes is of particular concern among ready-to-eat meat and poultry products. “Lm is known to form biofilms on food contact surfaces (FCSs) and non-food contact environmental surfaces and, as a result, persists on these surfaces despite aggressive cleaning and sanitizing,” FSIS states. “Once Lm has established a niche, it may persist in the environment for long periods of time until the niche is identified and eliminated.”
Escherichia Coli (E. coli)
Most E. coli strains are harmless and are an essential part of a healthy human intestinal tract. However, other strains pose a serious health risk and are dangerous foodborne pathogens transmitted by water, fruits and vegetables, raw milk, and meats. These products can be contaminated with E. coli during the growing process due to a contaminated water supply when cultivating the crops or as a part of the manufacturing process, where it may appear after washing or processing the raw material. E. coli biofilm may form in food storage environments due to suboptimal storage temperatures or as a result of improper cleaning and sanitization.
The growth of S. aureus biofilms is enhanced by various processing methods encountered in the food industry, such as improper sanitization and suboptimal storage temperatures. The emergence of methicillin-resistant S. aureus (MRSA) in farm animals has caused significant concern because animal-derived foods are a primary contamination origin for this resistant pathogen. Moreover, this pathogen can form biofilms on many different kinds of surfaces along the food production chain.
Related: The Importance of Disinfection in the Battle Against MRSA
Evidence of Biofilm on Food-Contact Surfaces
There are several ways to determine whether or not a biofilm has formed on a food-contact surface. For instance, there may be a slimy-feeling film on an otherwise clean appearing surface or a rainbow-like sheen on stainless steel surfaces. During routine microbiological testing, if a food plant discovers positive findings or an increase in bacterial counts, it may indicate biofilm formation. Additionally, adenosine triphosphate (ATP) bioluminescence devices can be used to detect the presence of organic materials (including food residue, dirt, or filth) on a surface. However, ATP may not consistently detect mature biofilms, as the embedded cells use much less energy and do not move as much as other microorganisms, thus producing less ATP. Therefore, in some cases, an ATP device may deliver a “pass” reading on a surface contaminated with biofilm. Finally, although a foul-smelling odor may not indicate the presence of biofilm, it can indicate that a surface or piece of equipment is not being cleaned and sanitized thoroughly and that there is a potential for biofilm formation.
How Can Biofilm Be Prevented or Eliminated?
Biofilm can’t be prevented or eliminated, but it can be managed. The best methods for this include:
- Adding biocides to a watering system (this can be beneficial in the dairy and agriculture industries).
- Mechanical cleaning systems and procedures.
- Modifying surfaces (there is no such thing as a biofilm-proof surface, but some are easier to clean, such as stainless steel).
- Pretreatment strategies, such as reverse osmosis.
Vital Oxide vs. Biofilm
Most ordinary sanitizers and disinfectants only effectively kill single cells, but not clumps (i.e., biofilms), because they only kill those on the outside. However, Vital Oxide is a class apart. Its innovative chemical structure allows it to knock down the cell wall protecting the organisms successfully. Each cell wall depends on proteins to form its walls. The cell produces amino acids (RNA) that act as building blocks for the protein; Vital Oxide can alter the amino acids in the cell. By doing this, Vital Oxide deprives the protein of its building blocks, and the cell wall crumbles. The organism within the cell wall then dies.
The oxidizer biocide within Vital Oxide is stabilized chlorine dioxide (ClO2). Chlorine Dioxide is more effective than conventional biocide chemicals such as ozone and chlorine. Both ozone and chlorine are consumed by other organic compounds, whereas chlorine dioxide is not. There are very few reactive compounds with chlorine dioxide, making this chemical compound much more selective. Other biocides may kill off free-floating bacteria, but they cannot prevent the bacteria within the colony from mutating and building up resistance. Chlorine dioxide chemically alters the cell, preventing it from combining with other cells and mutating, which is why Vital Oxide works against biofilms more effectively than other biocides.
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