BIOMATERIALS ASSOCIATED INFECTIONS - THE SCALE OF THE PROBLEM

The biomaterials used in the manufacture of implanted prosthetic devic es profoundly impair the host's ability to opsonise and phagocytose in vading microbes. As a result, while these devices generally provide ef fective relief from painful, crippling and life-threatening disorders, they can also induce vulnerability to infection in the recipients. Th e surfaces of the implants are susceptible to colonisation by microbia l biofilms. The cells in the biofilms are further protected against op sonophagocytosis and are also resistant to antibacterials. Device asso ciated infections thus tend to be refractile to antibiotic therapy and in many cases the device has to be removed before the infection will respond to treatment. Infection rates per implantation operation in to tally implanted devices, such as, artificial hips and knees, have fall en over the years to 1-2%. Devices that are partly implanted into body cavities or pass transcutaneously into tissues are particularly susce ptible to infection. For example, infection rates of 2.3-4 5% have bee n reported for central-line vascular catheters. The incidence of infec tion is related to the length of time the device is in place. Infectio n rates for urethral catheters indwelling for more than 28 days approa ch 100%. While several ingenious approaches are currently being taken to modify the surfaces of biomaterials, it has not yet proved possible to reduce the deleterious effects on the host or frustrate the surfac e colonisation mechanisms that microbes have evolved as a basic surviv al strategy in natural aquatic habitats.