Progress in the area of prevention of urinary catheter–associated infections is very limited compared with that in the vascular arena. Comparing and contrasting the pathogenesis of urinary catheter–associated infections to vascular catheter–associated infections elucidates the obstacles to prevention of catheter-associated UTI (CAUTI) (Table 2). While blood deposits thrombus on catheters, urine deposits organic molecules such as Tamm-Horsfall glycoprotein, a slimy protein of renal origin. The host proteins deposited from urine may facilitate attachment to the catheter by uropathogens, for Escherichia coli and related gram-negative organisms have hairlike projections that bind to the Tamm-Horsfall protein.50- 52 In the bloodstream, flow at the catheter tip is rapid, whereas in a catheterized urinary tract some stasis is usually present. Stasis, of course, predisposes to high levels of bacterial colonization. Additionally, while an intravascular catheter must pass through a skin wound, urinary catheters pass through a natural orifice. Thus, implementing sterile urinary catheter insertion techniques probably plays a lesser role in prevention of CAUTI, particularly in the case of long-term urinary catheters. In contrast to the relatively low numbers of skin flora present at the insertion site of a vascular catheter, contamination of the periurethral area with high numbers of bowel flora is very common.53,54 The most frequent causative agents of nosocomial CAUTI derive from the patient's colonic flora or from the hands of health care personnel; these organisms include E coli, enterococci, Pseudomonas, Klebsiella, Enterobacter, or Candida.4 The enteric gram-negative organisms found in the catheterized urinary tract are those that are commonly associated with multidrug resistance.4 Although most intravascular catheters remain in place for days to weeks, many patients wear indwelling urinary catheters for years, even for the duration of their lives. Thus, the difficulties of preventing CAUTI are compounded by catheter location, duration of catheter placement, numbers of organisms, and types of organisms typically contaminating the catheterized urinary tract.