Pathogenesis of infections related to intravascular catheterization.

Over the past few decades, there have been major technological improvements in the manufacture of intravenous solutions and the manufacture and design of catheter materials. However, the risk of infection in patients receiving infusion therapy remains substantial, in part because of host factors (for example, increased use of immunosuppressive therapy, more aggressive surgery and life support, and improved survival at the extremes of life) and in part because of the availability of catheters that can be left in place for very long periods. Microbial components of normal skin flora, particularly coagulase-negative staphylococci, have emerged as the predominant pathogens in catheter-associated infections. Therefore, efforts to prevent skin microorganisms from entering the catheter wound (such as tunnelling of catheters and use of catheter cuffs and local antimicrobial agents) are logical and relatively effective. The specific properties of microorganisms that transform normally harmless commensals such as coagulase-negative staphylococci into formidable pathogens in the presence of a plastic foreign body are being explored. For example, Staphylococcus epidermidis elaborates a polysaccharide adhesin that also functions as a capsule and is a target for opsonic killing. However, the interactions between microorganism and catheter that lead to adherence, persistence, infection, and dissemination appear to be multifactorial.