Chapter 3.6 : Diagnosis of Catheter-Related Bloodstream Infection: Differential-Time-to-Positivity Cultures and Catheter Tip Cultures

Abstract:

Intravascular (intra-arterial or intravenous) catheter insertions cause a break in the skin barrier amenable to infection. Table 3.6–1 lists the most common types of vascular and hemodialysis access catheters used for patient care that the laboratory may encounter. The continued presence of this foreign body predisposes further to infection, which can result from either colonization of the catheter by the cutaneous microbiota or, less commonly, hematogenous seeding due to hub contamination. Since infected catheters are usually exposed directly to sterile spaces, there is a risk that the infection will result in bacteremia. Intravascular catheter-related infections are a major cause of morbidity and mortality in the United States. The Infectious Diseases Society of America practice guidelines for management of these infections include culture of both catheters and blood ( 1 ). Central catheter infection may manifest as infection at the skin insertion site, as cellulitis along the soft tissues overlying the tunneled portion, or as bacteremia without evidence of external infection at either of these superficial sites. Bacteremia occurs secondarily to infection of the central catheter or as a manifestation of more serious complications, including septic thrombophlebitis or endocarditis. Laboratory confirmation of central catheter infection requires recovery of the same organism from a patient’s blood and from cultures of the catheter tip or from paired cultures drawn through the catheter lumen. Clinical policy should instruct physicians to submit blood cultures and either paired cultures from the catheter lumen or removed catheter segments to the laboratory for diagnosis of suspected catheter-related bloodstream infection. The most common infecting organisms are Staphylococcus aureus, enterococci, Candida spp., Pseudomonas aeruginosa, Enterobacteriaceae, and resident skin organisms, such as coagulase-negative staphylococci and Corynebacterium spp. The significance of the last group of organisms is not always clear, since the catheter is removed through the skin.