Biofilms play a pivotal role in healthcare-associated infections, especially those related to the implant of medical devices, such as intravascular catheters, urinary catheters and orthopaedic implants. This paper reviews the most successful approaches for the control and prevention of these infections as well as promising perspectives for the development of novel devices refractory to microbial adhesion, colonization and biofilm formation.

The use of implantable medical devices is a common and indispensable part of medical care for both diagnostic and therapeutic purposes. However, as side effect, the implant of medical devices quite often leads to the occurrence of difficult‐to‐treat infections, as a consequence of the colonization of their abiotic surfaces by biofilm‐growing microorganisms increasingly resistant to antimicrobial therapies. A promising strategy to combat device‐related infections is based on anti‐infective biomaterials that either repel microbes, so they cannot attach to the device surfaces, or kill them in the surrounding areas. In general, such biomaterials are characterized by antifouling coatings, exhibiting low adhesion or even repellent properties towards microorganisms, or antimicrobial coatings, able to kill microbes approaching the surface. In this light, the present overview will address the development in the last two decades of antifouling and antimicrobial biomaterials designed to potentially limit the initial stages of microbial adhesion, as well as the microbial growth and biofilm formation on medical device surfaces.

In modern medicine, artificial devices are used for repair or replacement of damaged parts of the body, delivery of drugs, and monitoring the status of critically ill patients. However, artificial surfaces are often susceptible to colonization by bacteria and fungi. Once microorganisms have adhered to the surface, they can form biofilms, resulting in highly resistant local or systemic infections. At this time, the evidence suggests that (؉)-usnic acid, a secondary lichen metabolite, possesses antimicrobial activity against a number of planktonic gram-positive bacteria, including Staphylococcus aureus, Enterococcus faecalis, and Enterococcus faecium. Since lichens are surface-attached communities that produce antibiotics, including usnic acid, to protect themselves from colonization by other bacteria, we hypothesized that the mode of action of usnic acid may be utilized in the control of medical biofilms. We loaded (؉)-usnic acid into modified polyurethane and quantitatively assessed the capacity of (؉)-usnic acid to control biofilm formation by either S. aureus or Pseudomonas aeruginosa under laminar flow conditions by using image analysis. (؉)-Usnic acid-loaded polymers did not inhibit the initial attachment of S. aureus cells, but killing the attached cells resulted in the inhibition of biofilm. Interestingly, although P. aeruginosa biofilms did form on the surface of (؉)-usnic acid-loaded polymer, the morphology of the biofilm was altered, possibly indicating that (؉)-usnic acid interfered with signaling pathways.

Antibiotic therapies to eradicate medical device-associated infections often fail because of the ability of sessile bacteria, encased in their exopolysaccharide matrix, to be more drug resistant than planktonic organisms. In the last two decades, several strategies to prevent microbial adhesion and biofilm formation on the surfaces of medical devices, based mainly on the use of antiadhesive, antiseptic, and antibiotic coatings on polymer surfaces, have been developed. More recent alternative approaches are based on molecules able to interfere with quorum-sensing phenomena or to dissolve biofilms. Interestingly, a newly purified ␤-N-acetylglucosaminidase, dispersin B, produced by the gram-negative periodontal pathogen Actinobacillus actinomycetemcomitans, is able to dissolve mature biofilms produced by Staphylococcus epidermidis as well as some other bacterial species. Therefore, in this study, we developed new polymeric matrices able to bind dispersin B either alone or in combination with an antibiotic molecule, cefamandole nafate (CEF). We showed that our functionalized polyurethanes could adsorb a significant amount of dispersin B, which was able to exert its hydrolytic activity against the exopolysaccharide matrix produced by staphylococcal strains. When microbial biofilms were exposed to both dispersin B and CEF, a synergistic action became evident, thus characterizing these polymer-dispersin B-antibiotic systems as promising, highly effective tools for preventing bacterial colonization of medical devices.