Device- Associated Infections

Abstract

A great variety of biomedical devices are used in patient care. Almost all hospitalized patients will have a vascular catheter placed to support administration of drugs, fluids, electrolytes, blood products, feeding solutions, or for haemodynamic monitoring. Many will also be exposed to urinary catheters, or tracheal tubes. There is also increasing use of a variety of prosthetic devices. Different biomedical devices have different infection associations. Examples of associations include cardiac pacemakers with Staphylococcus aureus blood-stream infection, contact lenses with amoebic keratitis, tampons with toxic shock, and historically, intra-uterine devices with pelvic actinomycosis. The most common causative organisms associated with device infections are bacteria (less commonly fungi). For many devices coagulase-negative staphylococci are the most frequent cause of infection. It is important to remember that an enormous range of microbes have been reported to cause device-associated infection. Biomedical devices predispose to infection through a wide range of mechanisms. These may include (depending on the device) traversing of anatomical barriers (such as the skin), protected niches for microbial proliferation, inappropriate immune activation, and provision of a surface(s) for biofilm formation. Few devices are completely inert. Most devices elicit an immune response, which depletes local complement levels and reduces oxidative killing by neutrophils, some directly damage tissues, and some release biologically-active products. There is much interest in the molecular mechanisms and physical interactions that underlie the formation of communal microbial structures on biomaterial surfaces. Many difference strategies have been proposed both to prevent, and to destroy microbial biofilms associated with biomedical devices. Complications associated with devices are most likely to be mechanical or infective. It is estimated that up to 25% of patients with a central venous catheter (CVC) will suffer a serious mechanical or infection related complication. Risk factors for infection include host, device, and operator factors. Extremes of age, co-morbidities such as diabetes, active infection at the time of insertion, and loss of relevant anatomical barriers to infection are host risk factors that apply to most devices. Operator risk factors include poor compliance with insertion or post-insertion ‘best practice’.