Urinary and intravascular catheters are two of the most used invasive medical devices; however, microbial colonization of catheter surfaces is responsible for most healthcare-associated infections (HAIs). Several antimicrobial-coated catheters are available, but recurrent antibiotic therapy can decrease their potential activity against resistant bacterial strains. The aim of this Review is to question the actual effectiveness of currently used (coated) catheters and describe the progress and promise of alternative antimicrobial coatings. Different strategies have been reviewed with the common goal of preventing biofilm formation on catheters, including release-based approaches using antibiotics, antiseptics, nitric oxide, 5-fluorouracil, and silver as well as contact-killing approaches employing quaternary ammonium compounds, chitosan, antimicrobial peptides, and enzymes. All of these strategies have given proof of antimicrobial efficacy by modifying the physiology of pathogens or disrupting their structural integrity. The aim for synergistic approaches using multitarget processes and the combination of both antifouling and bactericidal properties holds potential for the near future. Despite intensive research in biofilm preventive strategies, laboratorial studies still present some limitations since experimental conditions usually are not the same and also differ from biological conditions encountered when the catheter is inserted in the human body. Consequently, in most cases, the efficacy data obtained from in vitro studies is not properly reflected in the clinical setting. Thus, further well-designed clinical trials and additional cytotoxicity studies are needed to prove the efficacy and safety of the developed antimicrobial strategies in the prevention of biofilm formation at catheter surfaces.

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Nowadays, infections associated with urinary tract medical devices, have become a common health issue. The fact that their surfaces are prone to microbial colonization and biofilm formation is certainly a problem. As a result, these medical devices usage can be a source of extreme concern, especially for critically ill patients. Urinary tract related infections are among the most frequent HAIs comprising 27% in Europe and 36–40% in the USA. Among multiple strategies to fight those infections, biosurfactants as glycolipids can be a valuable tool for biofilm inhibition or disruption. In particularly, multiple in vitro studies concerning sophorolipids and rhamnolipids confirms the antimicrobial activity of those compounds. Further, sophorolipids or rhamnolipids potential role to prevent biofilm associated infections, using different surfaces like medical grade silicone as an example of common material used in catheters and stents fabrication, shows the capacity of those biosurfactants in reducing the adhesion and biofilm formation. Overall, sophorolipids and rhamnolipids due to their multiple antimicrobial/anti-adhesive effects might be an interesting approach to fight urinary tract medical devices associated infections.

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<p>Biofilm development on medical devices is of particular concern and finding new strategies for preventing surface colonization and infection development are urgent. Antimicrobial biosurfactants such as rhamnolipids (RLs), emerge as one possible solution due their lack of resistance development. Using nanoparticles as delivery systems for these compounds may be a promising alternative in the context of biofilm-infections control. As such, the aim of this study was to encapsulate RLs into chitosan nanoparticles (RLs-NPs), test their antimicrobial activity and their biocompatibility profile.</p> <p>Blank nanoparticles (b-NPs) and RLs-NPs were prepared by ionic gelation. For particles characterization, zeta potential, size distribution and encapsulation efficiency were performed. Minimal inhibitory concentration and biofilm inhibition ability were evaluated towards Staphylococcus aureus (ATCC 25923). To access NPs cytocompatibility the in vitro tetrazolium dye assay (MTT) and morphology observation were performed with a mouse fibroblastic cell line (L929).</p> <p>RLs-NPs presented an encapsulation efficiency of 74.2±1.3%, a size ranging from 300 to 400 nm and a zeta potential of  37±1 mV. The minimum inhibitory concentration of RLs-NPs was 130 mg/mL and a 99% biofilm inhibition was achieved with these NPs meaning that their antimicrobial activity is also effective towards sessile bacteria. When compared to control, cell cultures grown in the presence of RLs-NPs presented no significant differences regarding the MTT reduction values and morphology analysis, suggesting that NPs up to 500 mg/mL did not significantly interfere with viability and proliferation.</p> <p>The results revealed that the RLs-NPs were able to inhibit bacterial growth showing adequate cytocompatibility and might become, after additional studies, a possible approach to fight S. aureus biofilm associated infections.</p> <p><strong>Acknowledgments: </strong>Support for this work was provided by FCT through Portuguese government, PTDC/BTM-SAL/29335/2017 and Pest-UID/DTP/04138/2019</p>