Prevention of intravascular device-related infections

Therefore, besides strict hygienic rules during insertion of the device, the development of new materials able to counteract microbial adhesiveness and colonization has become a critical issue in recent years. The two principal approaches to prevent microbial adhesiveness are (1) the development of polymers with antifouling properties, and (2) the development of polymers with antimicrobial properties. Such materials either repel microbes (antifouhng) or kill bacteria (antimicrobial) present in the surface proximity. 

In the first three approaches, the polymer acts as a carrier for the antimicrobial agent that once released can exert its action (antimicrobial agent-releasing polymers). In the first case the antibiotic is adsorbed mainly on the device surface, in the second case the drug is physically entrapped, while in the third case the antibiotic is grafted by labile bonds. In the fourth approach, the whole polymer (the bulk and the surface) is intrinsically antimicrobial and exerts its killing action when microorganisms contact the surface. These polymers are often called biocidal polymers. 

In the following sections, antifouling and antimicrobial PUs will be presented in relation to their application for preventing intravascular device-related infections. 

Recently, to obtain antifouling materials, segmented PUs having the same hard domain but a variable soft domain have been synthesized. The soft phase was constituted by polypropylene oxide (PPO), polycaprolactone (PCL), or poly-L-lactide (PLA). PCL- and PLA-containing PUs reduced the adhesion of S. epidermidis compared to the PPO-containing PU this ability is presumably related to their greater hydrophilicity. 

Several hydrophilic coatings were applied to PUs to increase surface hydrophilicity, including poly(ethylene glycol) (PEG), hyaluronan, dermatan sulfate, and heparin. 

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Pearson, M. L., Guideline for prevention of intravascular device-related infections. Part 1. Intravascular device-related infections An overview. Part II. Recommendations for the prevention of nosocomial intravascular device-related infections, Am. J. Infect. Control, 1996 24(4) 262-293. 

Dmg-releasing PUs can be considered the first milestone in the prevention of intravascular device-related infections. Already, their clinical application has contributed to decreasing infection risk, mortality rate, and patient morbidity. However, the use of these drag-releasing polymers has elicited concerns in terms of durability and possible local emergence of resistant microorganisms. 

O Grady NP, Alexander M, Bums LA, et al. Guidelines for the prevention of intravascular catheter-related infections. Am J Infect Control May 2011 39(4 Suppl. l) Sl-34. Francolini 1, Donelli G. Prevention and control of biofilm-based medical-device-related infections. FEMS Immunol Med Microbiol August 2010 59(3) 227-38. 

This chapter will be focused on antimicrobial PUs for intravascular applications. First, a classification of the types of PU intravascular devices and their impact in the medical held will be inhoduced. Then, a survey of infections associated with intravascular devices in terms of incidence, etiology, and pathogenesis will be presented. Next, management of device-related infections and the role of modified PUs in preventing intravascular device-related infections will be discussed. Finally, the future direction of novel antimicrobial polymers as biomaterials for the development of devices preventing biofilm-based infections will be described. 

A crucial feature required for a successful application of PUs as biomaterials is their ability to prevent microbial colonization. Indeed, any implanted biomaterial is known to have the potential to put the patient at high risk of infection. In case of intravascular devices, the development of device-related infections may result in life-threatening consequences for the patient. 

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