Biofilms pose a serious challenge in various industries affecting product quality as well as human health. The presence of these biofilms can complicate operations and lead to significant contamination risks. However, biocides with proven efficacy against biofilms have been developed that aid in reducing contamination risks. In this article, we will explore biocide efficacy against biofilms, the challenges posed by biofilms and why testing is essential to ensure your biocides are effective.

The challenge of biofilm contamination

A biofilm is a community of microorganisms that bind to each other and grow on surfaces. The microbial cells in a biofilm are covered by a slimy, protective layer made of extracellular polymeric substance (EPS). They can form on various surfaces ranging from industrial pipes to medical devices and pose a major challenge to cleanliness and sterilization. Unlike free-floating microorganisms, biofilms are generally resistant to ordinary cleaning methods.

Surface contamination caused by biofilms can result in serious consequences such as operational downtime, product recalls and health risks. Biofilms contaminate food products which result in food spoilage or food-borne illnesses. They also cause nosocomial infections in hospital settings, particularly in immunocompromised patients. Treatment of such hospital-acquired infections is very challenging due to their high tolerance to antibiotics. Thus, ensuring biocide efficacy against biofilms is essential for overcoming these challenges.

Importance of biocides in controlling biofilms

Biocides are chemicals that inactivate or inhibit the growth of microorganisms. They play an essential role in industries where hygiene and contamination control are of utmost importance. However, the protective structure of biofilms makes them difficult to penetrate and hence specialized biocides are required for the effective degradation of the biofilm matrix and the elimination of embedded microorganisms.

Role of biocides in biofilm control

How do biocides work against biofilms?

Biocides must achieve two key tasks to effectively control biofilm formation: penetrate the biofilm matrix and kill the embedded microorganisms.

1. Disruption of the biofilm matrix 

• The initial step of biocide action is the destruction of the protective EPS (extracellular polymeric substance) matrix that coats the cells. Some biocides especially enzymes and surfactants are formulated to disrupt this matrix, thereby letting active antimicrobial agents diffuse further into the matrix. If this disruption does not take place, biocide efficacy against biofilms will be limited to the outer layers, leaving the inner cells untouched.

2. Targeting microbial cells

• Upon penetration, the biocide has to effectively kill the microbial cells. This is accomplished through various mechanisms such as protein denaturation, destruction of cell membranes and general enzyme functioning.

Factors that affect biocide efficacy

Several factors impact biocide efficacy against biofilms, including:

Surface type

• The type of surface on which the biofilm forms such as porous or non-porous may influence the biocide efficacy against biofilms.

Biofilm maturity

• The stage of biofilm development can also influence the efficacy of a biocide. Young biofilms are generally thinner and less structured. Hence they are usually most susceptible to biocides. As the biofilm matures, it becomes more complex with increased layers of microorganisms and a more compact EPS matrix, making penetration and microbial eradication by the biocide difficult.

Biocide concentration and contact time

• Biocide’s concentration and its contact time with the biofilm also present crucial effects on biocide’s efficacy. While higher concentrations may enhance biocide efficacy against biofilms, they can also pose safety risks and surface damage. Finding the balance between concentration and contact time should be sought to achieve control of the biofilm while minimizing the possible downsides.

Environmental conditions

• Factors like pH, temperature and the presence of organic matter could impact the performance of biocides. For example, chlorine-based biocides lose their effectiveness in the presence of organic matter. Other biocides may require specific pH levels to remain active. Tailoring the biocide to the environmental conditions aids in controlling biofilm growth.

Biofilm composition

• Biofilms are an amalgamation of different species of microorganisms including bacteria, fungi or algae. The susceptibility of each species to a particular biocide may vary greatly. Some microorganisms may inherently produce biofilm components that are more resistant to biocides and require a combination of different antimicrobial agents to eliminate all the microbial cells.

Challenges in biofilm penetration and elimination

• A major challenge in biofilm control is to achieve successful penetration of the biocide through the biofilm matrix. The EPS acts as a barrier and it minimizes the diffusion of the biocides, hence allowing the survival of the microorganisms within the biofilm. Therefore, biocide efficacy against biofilms must be thoroughly tested for their penetration action and complete microbial elimination.

Testing biocide efficacy against biofilms

• Laboratory testing of biocide should be performed before launching the product in the market. This practice ensures that biocides will effectively reduce biofilms under real conditions. If the biocides are not tested properly, there is a likely risk of underperformance, resulting in contamination issues and potential product recalls.

Standard testing methods to assess biocide efficacy against biofilms

Several standard test methods are available to measure biocide efficacy against biofilms. International organizations such as ISO, ASTM and EN provide these comprehensive test standards. They set the guidelines on the test conditions, the selection of test organisms, materials to be used as surfaces and the concentrations of test biocide whose efficacy is to be tested. Adhering to these standards ensures the performance of biocides under realistic conditions and thus increases replicability. Relevant test standards include:

• ASTM E2799: Standard to test the efficacy of disinfectants against Pseudomonas aeruginosa biofilm using the Minimum Biofilm Eradication Concentration (MBEC) assay.

• ASTM E2871: Test method for assessing the efficacy of disinfectant against biofilm grown in the CDC biofilm reactor using the single tube method.

• EN ISO/TS 15883-5: Test evaluates the biocidal efficacy of a disinfectant and biomass reduction against a standard biofilm.

• ASTM E2196: Standard test method for quantification of Pseudomonas aeruginosa biofilm grown with medium shear and continuous flow using rotating disk reactor

Regulatory requirements for biocide efficacy testing

Global regulatory standards for biofilm testing

Regulatory agencies like the EPA (Environmental Protection Agency) or the ECHA (European Chemicals Agency) have strict biocide efficacy testing requirements. Manufacturers must comply with these standards to ensure their products are effective and gain approval for market release.

Best practices for meeting regulatory demands

Biocide developers should invest in testing that includes a range of biofilm-forming organisms, surface types and environmental conditions to meet regulatory demands. Collaborating with an accredited laboratory ensures compliance with global standards in all testing procedures.

Benefits of biocide testing

The benefits associated with rigorous testing of biocide efficacy against biofilms include ensuring real-world effectiveness, product performance optimization and boosting consumer trust. Products that pass the biofilm test are more likely to be approved and successful in the market.

As biofilms continue to pose challenges across various industries, the development of more effective biocides will be critical. This development may further be driven by advancing biofilm research and biocide formulations toward more innovative solutions for biofilm control. Reliable testing is essential for ensuring biocide efficacy against biofilms. If standardized test methods are used and regulatory requirements for product registration are met, companies can launch products with complete confidence that the performance in the field will live up to expectations.

At Microbe Investigations Switzerland, we offer antimicrobial testing services to validate the efficacy of your biocidal product against biofilms. Our expertise in Biocide testing helps ensure that your products meet regulatory requirements and perform effectively in real-world applications. 

Contact us today to learn more about our biofilm testing services or to schedule a consultation.