Biofilms, biomaterials, and device-related infections

The chapter “History of Biomaterials” at the start of this book documents the development and design of indwelling materials for medical and dental purposes. The initial design criteria in the choice of materials were pragmatic, and based on the necessary mechanical properties required to fashion a functional device. Orthopedic implants require strong materials for weight-bearing, and articulating surfaces such as joints require durability and resistance to wear. Stents and shunts require flexibility and patency, and sutures require a high tensile strength yet also must be flexible enough for intricate manipulation. As the devices became more sophisticated and developments in materials science provided more options for manufacture, implants are being used more frequently and with longer anticipated lifetimes. Concurrently, the design process increasingly incorporated biocompatibility and comfort into the design criteria. However, with longer lifetimes, the more frequent use of invasive surgical procedures involving indwelling devices and biologically-friendly materials, there has been a rise in the number of incidences of device-related infection. Urinary catheters have been estimated to account for 30% of all nosocomial infections (Gould et al., 2010). Between 66 and 88% of these occur after urinary catheterization (Wong, 1983). It is also reported that almost 100% of catheterized patients develop an infection in an openly draining indwelling catheter which has been in place for four days or more (Wong, 1983). For some procedures, such as orthopedic joint arthroplasties, the diagnosed surgical site infection rates are relatively low (between 1% and 2%; Hsieh et al., 2009); however, the increasing number of patients undergoing joint-replacement surgery translates to large numbers of patients afflicted with the consequences of complicating infections per year. Furthermore, infection of artificial joints can be devastating, since oral or IV antibiotic therapy frequently fails to resolve the infection, with the only remaining course of action being surgical debridement or partial or total revision. These two examples, the first with very high numbers of patients but of lesser severity in terms of impact to the individual, and the second, low numbers but severe patient impact, reflect the incentive to pursue a third design criteria – that of infection resistance – into materials and devices (Maki and Tambyah, 2001). In the following sections we will discuss the role of bacterial biofilms in infection, and the growing literature highlighting biofilms as an important cause of device-related infectio