Biofilms are complex microbial communities that bacteria form on various surfaces, including body tissue, medical implants, and catheters. They consist of bacterial cells embedded in a dense matrix of exopolysaccharides, proteins, and DNA. This matrix not only holds the colony together but also protects it from external influences, such as antibiotics and the body's immune system.

Bacteria form biofilms as a defense mechanism in response to stressful conditions, such as nutrient deficiency or the presence of antimicrobial agents. Within the biofilm, bacteria can exchange genetic material, facilitating the spread of antibiotic resistance genes.

Why antimicrobials are ineffective against biofilms

Traditional antibiotics are often ineffective against bacteria found in biofilms for several reasons:

• Physical barrier: The biofilm matrix prevents the penetration of antibiotics, reducing their concentration to a level insufficient to kill bacteria.

• Persistent cells: Within the biofilm there are so-called “persistent” cells – bacteria in a dormant state that are less sensitive to antibiotics.

• Genetic adaptation: Bacteria in biofilms have an increased capacity for mutation and gene exchange, which contributes to the development of antibiotic resistance.

These factors complicate the treatment of biofilm-related infections and often lead to chronic diseases.

How bacteriophages destroy biofilms

Bacteriophages are viruses that specifically infect bacteria. They have several mechanisms of action that make them effective against biofilms:

• Matrix penetration: Phages are able to penetrate the biofilm matrix and infect bacteria inside.

• Enzyme production: Some bacteriophages produce enzymes that break down biofilm components, facilitating access to bacteria.

• Replication within bacteria: After infection, bacteriophages replicate within bacteria, leading to their destruction and subsequent spread of phages to other pathogens.

Studies have shown that using cocktails of multiple bacteriophages can be particularly effective in disrupting biofilms, as different phages can attack different bacterial strains simultaneously.

Synergy of bacteriophages and antibiotics in the fight against biofilms

Although antibiotics are often ineffective against biofilms, they shouldn't be completely dismissed. Current research shows that the best results come from the combined use of bacteriophages and antibiotics. This strategy leverages the strengths of both approaches: phages can penetrate biofilms, disrupt their matrix, and kill some bacteria, paving the way for antibiotics to then reach vulnerable microorganisms.

This synergy is particularly useful in the treatment of chronic or hospital-acquired infections, where biofilms play a key role. For example, a study conducted by a team from the University of Copenhagen (2021) showed that applying bacteriophages to biofilm-infected implants increased the effectiveness of subsequent antibiotic therapy severalfold.

Interestingly, some bacterial viruses can alter the physiological state of pathogens, making them more sensitive to antibiotics, even those to which they were previously resistant. At the same time, antimicrobials, by reducing bacterial density, can facilitate the work of phages, which spread better in thinner environments. Thus, both agents—antibiotics and bacteriophages—can act synergistically.

The potential of this type of phage therapy in combination with antibiotics is already being explored in a number of clinical projects, and the initial results are encouraging. This opens new horizons in the treatment of resistant infections, where biofilms are a major obstacle to patient recovery. This approach is particularly promising in urology, orthopedics, and the treatment of chronic wounds.