Biofilm Formation on Intravascular Catheters and Methods of Infection Prevention

Nancy Moureau PhD, RN, CRNI, CPUI, VA-BC

Catheter-associated infections remain a significant concern in healthcare, emphasizing the need for advancements in catheter materials that reduce the risk of biofilm formation and subsequent infections.

Intravascular catheters play a crucial role in medical treatment and interventions, yet their use often leads to complications, including infections linked to biofilm formation. Biofilms create a protective environment for bacteria, allowing them to resist host defenses and conventional antimicrobial treatments. Bacterial biofilms play a role in the development and persistence of catheter-related infections (CRIs). A biofilm is a structured community composed primarily of bacteria that adheres to surfaces and produces a protective extracellular matrix, creating a highly resilient environment. In the context of intravascular catheters, biofilm formation poses a serious threat. When a catheter is inserted into the body, bacteria can quickly adhere to its surface and form a biofilm.

The process of biofilm formation follows a sequence involving bacterial attachment (which quickly becomes permanent), intercellular communication, and the chemical synthesis of polysaccharides, ultimately resulting in the maturation of the biofilm. This process can be likened to erecting a tent over a community of bacterial colonies, providing insulation against the body's natural immune defenses. Once biofilm maturity is achieved, the process becomes irreversible. This biofilm provides a protective shield, making it challenging for the host's immune system and antimicrobial agents to destroy the bacterial colonies effectively. Bacteria in the biofilm colony grow to critical mass, releasing bacteria into the bloodstream, and may result in systemic infection. These biofilm-enabled bacteria are strengthened up to 1000-fold, resisting any antibiotic treatments. Oftentimes, the only suitable control measure for biofilm-associated infection is the removal of the intravascular catheter.

Challenges posed by biofilm:

1. Increased Infection Risk: Biofilm formation on the surface of intravascular catheters creates a conducive environment for bacterial colonies to thrive. This significantly raises the risk of infections, as the protective matrix formed by the biofilm shields bacteria from the host's immune system and antimicrobial agents.

2. Resilience to Antibiotics: Once a biofilm matures, the bacteria within it become highly resistant to antibiotic treatments. The protective nature of the biofilm prevents antibiotics from effectively reaching and eliminating bacterial colonies. This resilience can make traditional antibiotic therapies ineffective against infections associated with catheters.

3. Systemic Spread of Infections: The detachment of biofilm fragments from the catheter surface can be detrimental. These fragments enter the bloodstream, allowing bacteria to disseminate throughout the body. This increases the risk of systemic infections, which can be severe and life-threatening.

4. Impaired Immune Response: The biofilm not only shields bacteria from external threats but also hinders the host's immune system from recognizing and eliminating the bacterial colonies effectively. This impaired immune response further complicates the control and resolution of infections associated with intravascular catheters.

5. Persistent Infections: Biofilm formation establishes a persistent source of infection. Even if initial treatments manage to reduce bacterial populations temporarily, the biofilm allows rapid re-establishment of bacterial colonies, leading to recurrent and persistent infections.

6. Complications during Catheter Removal: In some cases, the only effective measure to control biofilm-associated infections is the removal of the intravascular catheter. However, catheter removal comes with its own challenges and risks, including the potential for complications during removal and the need for a replacement catheter. Prolonged difficulty in the replacement of vascular access can jeopardize the patient and contribute to increased morbidity and mortality.

More than 60% of CRIs are related to the release of biofilm-enabled bacteria. To mitigate the risk of CRIs, ongoing research is focused on the development of materials that prevent bacterial attachment and biofilm formation. Catheter material enhancements to prevent infection incorporate polymers that coat, impregnate, and form composites that have antimicrobial and/or anti-thrombotic characteristics. Some of these enhancements are metal (e.g., silver, copper), chemical agents (e.g., chlorhexidine), antibiotics (e.g., rifampin, mithramycin), and hydrophobic and hydrophilic materials. Changes to the catheter surfaces can enhance infection prevention by reducing bacterial attachment, the first stage before biofilm production.

Bacterial adherence to catheter surfaces is a key precursor to biofilm formation. Catheter materials create an environment for bacterial attachment that is more favorable or less favorable to attachment and biofilm development, depending on their physical hydrophobic or hydrophilic properties. According to Treter and associates, bacterial adherence favors hydrophobic surfaces more than hydrophilic ones. The slippery surface of hydrophilic materials reduces the likelihood of bacteria adherence. Studies have demonstrated a significant decrease in bacterial colonization on hydrophilic catheters and, thus, reductions in biofilm production in comparison to traditional polyurethane or hydrophobic catheter materials.

Hydrophilic catheter materials possess unique characteristics that make them promising for infection prevention. These materials are water-attracting, aiming to minimize the foreign body response, decrease bacterial adherence, and consequently limit biofilm formation. The water-attracting properties of hydrophilic materials contribute to a self-cleaning effect, flushing away bacteria and preventing adherence to the catheter surface. The reduced friction during catheter placement minimizes trauma to the surrounding tissues, leading to a decreased inflammatory response. This, in turn, creates an environment less favorable for bacterial colonization. While research regarding hydrophilic catheter materials show promise in infection prevention, further high-level research into clinical outcome performance must be performed.

In summary, biofilm formation on intravascular catheters is detrimental as it increases the risk of infections, reduces the effectiveness of antibiotic treatments, facilitates the spread of bacteria throughout the body, impairs the host's immune response, and leads to persistent infections. Managing and preventing biofilm formation are critical aspects of ensuring the safety and efficacy of intravascular catheter use. By addressing the foreign body response and reducing bacterial adherence, hydrophilic materials contribute to a safer catheterization experience and decrease the risk of associated infections. Continued research and collaboration between scientists, engineers, and healthcare professionals are essential to translate these innovations into practical and effective strategies for infection prevention in patients requiring intravenous medical treatment. The advancement of catheter materials designed to mitigate foreign body response, diminish bacterial adherence, and restrict biofilm formation constitutes a pivotal stride in the proactive prevention of catheter-associated infections.

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